HOW TO THREAD A BCD TANK STRAP

 

How many times did it happen that, arriving to the diving site, you find out that your BCD’s tank cam band is open and unconnected?

 

Did you know that you can re-thread it by yourself, without always asking a divemaster or an instructor for help? 

 

This short video shows you how to do it!

 

 

 

 

REVERSE PROFILES IN RECREATIONAL DIVING

Many of us, reading our Open Water Diver manuals (including PADI and CMAS) have been instructed and warned about the danger of diving s.c. reverse profiles.

Briefly explained, reverse profiles occur when, within a single dive, the latter portion of the dive is deeper than the earlier portion or, in the case of repetitive dives, the repeat dive is deeper than the earlier one.

 

Although the rule against reverse dive profiles has been (and apparently still is) widely accepted and taught by major recreational diving agencies, it is not clear where did this rule came from and which was the scientific motivation behind it. Sure thing, historically this limitation could be explained by the use of dive plan tables and electronic dive planner that were only in the condition of calculating bottom time and nitrogen loading only based on the maximum depth and time figures.

With this in mind, in the year 1999 the Smithsonian Institution and AAUS (American Academy of Underwater Sciences) called a Workshop with the purpose of investigating, among others,  if there is any physiological basis (read “DCS incidence”) for the rule against reverse profiles ( Reverse Dive Profiles Workshop, Washington DC, October 29 and 30, 1999).

The results of this study, that considered modern bubble decompression models, were:

• Historically neither the U.S. Navy nor the commercial sector have prohibited reverse dive profiles. 

• Reverse dive profiles are being performed in recreational, scientific, commercial, and military diving. 

• The prohibition of reverse dive profiles by recreational training organizations cannot be traced to any 
definite diving experience that indicates an increased risk of DCS. 

• No convincing evidence was presented that reverse dive profiles within the no-decompression limits 
lead to a measurable increase in the risk of DCS.

Within this research, the possible increase of DCS cases possibly connected to reverse profiles was explained with the fact that very often reverse profiles are associated to repetitive dives on multiple days activity and connected nitrogen exposure.  

The conclusion of the study was that if diving within no decompression limits and less than 40 meters, and within a maximum depth difference of 12 meters, the current evidence does not show any demonstrable increase in risk of DCS.

With this in mind, and with the generic commercial spread of dive computers with algorithms capable of adequately calculate bottom time and residual nitrogen loading for reverse profiles, today the only reason for avoiding reverse profiles in recreational diving seems to be purely based on the necessity of maximizing the dive duration.

In fact, even if apparently not relevant for DCS, reverse profiles  still significantly reduce the available bottom time, and this is for sure a valid reason for avoiding them when possible: for sure, when we are on holiday, we want to maximize our fun and to stay below water as long as we can!

One last consideration: the position of the Smithsonian Institution and AAUS is not globally shared and there have been more recent studies showing different results, even though based on animal experiments (The relative safety of forward and reverse diving profiles. S. McInnes, C. Edmonds, M. Bennett, UHM 2005: VOL 32, ISSUE #6).

Nonetheless, the results of the 1999 Workshop are still widely accepted, among others, also by Divers Alert Network (DAN).

I share this article based on my best knowledge and research on public documentation as well as literature in my possession. If any of you fellow divers out there, especially tech divers, do have any further information or authoritative source, I would be happy to further investigate and discuss with you!

 

 

CONSEQUENCES OF RAPID ASCENT AFTER THE SAFETY STOP

Many times, in my professional activity (mostly in the role of dive guide), I witness the inexplicable behavior of divers who, after a perfect safety stop at 5 meters performed in very good buoyancy, rapidly swim to the surface or even worse just inflate the BCD and pop up uncontrolled. 

These divers are probably convinced that after the safety stop there is no more risk and it’s possible to return rapidly to the surface and thus to the boat… Well this could not be more wrong! 

To perform a safety stop does not mean to eliminate every risk: in fact, the last 10 to 5 meters before surfacing are the most stressful for our body, in terms of percentage pressure change and connected gas volume differential. 

If we consider the Workman critical ratio 1,58:1, we can easily understand that a rapid ascent from 5 - 6 meters is at the very limit of this value! Moreover, the most modern VPN and RGBM decompression models imply the constant presence of bubbles in the body tissues, and in a previous article we learned that a full washout (off-gasing) of bubbles relevant for DCS only occurs in the 12 - 24 hours following the dive. So, given the presence of bubbles in the tissues while we still are underwater, the sudden pressure decrease caused by a rapid ascent from 5 meters could trigger the production and growth of bubbles potentially relevant for DCS. 

Furthermore, a rapid ascent from 5 meters is not only relevant in terms of DCS, but also with reference to pulmonary injuries and barotrauma, such as reverse squeeze. In particular we shall always keep in mind that, if we surface holding the breath with full lungs, a depth change of only 1,2 meters is sufficient to cause lungs over-expansion! 

 

Finally, considering, the massive pressure change in this delicate phase, it is recommendable to choose an ascent speed even slower than the 9 m/s recommended by many training agencies. Considering an ascent rate of 6 m/s, we should take at least one minute to surface from 5 meters! 

No need to say that in this phase, perfect buoyancy is the most important skill to be mastered, so keep training and, if necessary, join dedicated buoyancy courses.

KEEP DISTANCE!

As many of you know, this Summer I had the opportunity of working by OmniSub, one of the historical diving center of the Isle of Elba.

As a tradition in Italy, in the month of August the island was rather packed: as a consequence, also the maritime traffic has been very high.

This situation caused a lot of stress in particular for our non diving boat crew, whose main task during this crazy period was to shout and wave to unresponsible boat drivers who rushed at high speed just a few meters away from our boat, thus putting at risk the safety of the divers below who in the worst but not impossible case could be hit by the hull or even by the propeller of boats moving right above their heads.  

📸 (c) DAN Europe

 Of course generally every diver and diving center staff member is very well educated about the obligation to use a “diver-down” or “alpha” flag and a surface marker buoy. Nevertheless, the above described incident tipology is generally caused by lack of attention or ignorance: with reference to this second point, unfortunately in Italy is it possible to rent any boat up to 40hp, even without any licence, under the condition of being at least 16 years old and to remain within six miles form the coast. Surprisingly, a display of knowledge of the most basic national sea traffic regulation is not a requirement for getting the boat.

 

For this reason, I grab this opportunity to make you aware about the ITALIAN regulation about diving warning signals and minimum distance from divers and diving boats.
 The subject was originally regulated by the DPR 1639 from 02.10.1968, art. 130, that states as follows:

 

• scuba divers must use a float equipped with a red flag with a diagonal white stripe (“diver-down” flag). If diving from a boat, the flag bust be lifted on the boat;
• scuba divers can move within a range of 50 meters from the boat or from the float.

In addition, in the year 2003 a note from the Corps of the Italian Port Authorities imposed to boats and vessels a minimum distance of 100 meters from diving warning buoys and diving boats.

Nowadays the subject is regulated by the D.M. 146 from 29.07.2008, art. 91 that, in addition to the above mentioned rules, requires every diver to bring along a personal DSMB.

It is important to stress out that the violation of the rules concerning minimum distance by boat drivers lead to criminal prosecution even if no incident or injuries occur.

Eventually, here a few safety tips for divers:

• always surface as close as possible to the diving boat;
• use an SMB if you are not able to locate the boat. If you di not know how to deploy an SMB; please refer to my previous post available here: https://www.facebook.com/741846475/videos/10157262944171476/;
  
• train your buoyancy, avoid uncontrolled ascents and always look up before surfacing.

 

PERFORMING SKILLS: KNEELING OR NEUTRALLY BUOYANT?

I have being discussing many times with colleagues, friends and students whether it is better to demonstrate and learn OW skills in a neutrally buoyant position or on the knees, and I can already anticipate you that without any doubt I opt for the first solution. Here is why.

First of all, let me clarify that for me neutral buoyancy does not necessarily mean being “perfectly” neutrally buoyant from the first second we hit the water, but just horizontal position. The first skills can be comfortably achieved in slightly negative buoyant position, with the tip of the fins and belly or hands touching the bottom. Progressively, by practicing buoyancy skills as oral inflation and fin pivot, the student will improve his horizontal neutral position in the water.

📸 La Palma Diving

The above described slightly negative position offers the advantage for the student of practicing skills in a more realistic dive position, but still keeping the pool bottom as a reference in case of lost of balance. In fact, when practicing skills in a resort pool there is normally no problem in keeping the position on the knees; on the contrary, if we must teach skills in a wavy confined open water session for the students it will be easier to keep the balance in an horizontal position with the tip of the fins touching the bottom. The students in fact will have the possibility of helping themselves with the hands, e.g. by holding a big rock, and they will not be pushed away by the waves as it could happen in a knee position as a consequence of the bigger body area exposed to the waves. In consideration of the above, I do not see any problem in connection with students ratio as the group will be more compact and stable.

Moreover, being used to horizontal position, in open water environment the student will be already used to a correct horizontal trim and will not tend to put himself in a vertical position in order to perform skills. This normally works also in relation with simple DSD dives.

Furthermore, speaking about a realistic training scenario with very short time available due to holiday schedule, learning in an horizontal position is not more difficult that learning on the knees, it is just a matter of initial set up.

Of course much of this depends by how the instructor himself was trained to perform skills during his IDC: many instructors that learned to perform skills on their knees will find inconvenient to demonstrate in neutrally buoyant position, just because they never trained how to do it properly. In fact, the demonstration of some skills (think about BCD or weights system removal and replacement) changes drastically if you chose knee or an horizontal position.

For this reason, in my personal case, I decided to opt for an IDC where I could learn how to demonstrate skills in a neutrally buoyant position: switching from neutral buoyancy to kneeling position is easy, but the opposite can be tricky and needs some training.

Some last considerations:

• as the training standards of major agencies do not impose any position, the instructor must be clever enough to "read" his students and to choose the position that better adapts to his students’ water skills, in order them to complete the course having fun and without stress;

• the surrounding underwater environment and the sea bottom structure also influence the demo position: if teaching in a place full of corals where you only have available a patch of sand 3m x 3m, it will be difficult for both instructor and student to lay on their belly so the only solution, at least in the beginning, would be to perform skills in kneeing position. This is valid in particular in the case of DSD in tropical destinations where no pool is available;

• if the instructor opts for a position, he shall perform all the skills in that position. In other words, if you go for neutral buoyancy, you shall teach all the skills in neutral buoyancy and not some in one position and some in the other, otherwise this could be potentially misleading for the student.

And you? How did you learn basic skills during your Open Water Course?

If you are an instructor, how do you teach skills to your students?

DAN RELEASES NEW COVID-19 MEDICAL FORM

Following the latest MIT recommendations DAN releases a new medical statement form for diving during covid-19.

Click on the picture below for free download ⤵️

PLASTIC HOSE PROTECTORS

📸 (c) User Szdavid

Almost every new regulator we buy comes with plastic hose protectors. On the other hand, expecially among tech divers, we often see “naked” configurations without any sort of protection on the hoses.

Plastic protectors have basically one simple purpose: to protect the hoses from exagerated bending and crimping in one of the weakest positions of the construction, next to the joints where the metal plugs meet the rubber.

Nevertheless nowadays flex hoses are becoming a more and more popular standard: this particular kind of polymer or carbon braided hose offers greater resistance to bending, preventing the hose from crimping and thus making hose protectors useless.

In any case, whether you use rubber or braided hoses, I would discourage the use of plastic protectors for the following reasons:

1. As said above, plastic protectors shield the weakest part of the system, which is also the most likely to fail. If we remove the protectors it will be easier to spot any possible small gas leak coming from a damaged o-ring, oxidized thread or swivel. In fact, hose protectors could  partially dam small leaks, making a potentially serious problem invisible during the bubble check in shallow water. 
2. Hose protectors are the perfect place for salt, dirt and sand to collect, accelerating the oxidation process of metal parts of the hose. This is why every time we rinse our regulator we shall remove the protectors, which leads to no. 3 & 4.
3. Some protectors are very tight: every time we remove them for rinsing properly our gear we put a lot of mechanical stress on the metal joints and threads of our regulator, increasing the risk of damage and accelerating the wear process. In addition, some protectors are made out of very hard material and from time to time I have seen hoses bending and crimping at the free end of these protectors!
4. On the contrary, loose protectors tend to slip down along the hose by themselves, thus not serving their purpose and being completely useless.

So now you might ask yourself: how do I prevent my rubber hoses from bending next to the joints?
 

Simple, look after your equipment! This is all about pretty expensive gear that provides us life support, basically we are speaking about the most important piece of equipment, so take care of your kit, do not drag the hoses when moving the assembled gear, rinse it properly after use, and pack the regulator properly when traveling!

OFF-GASING & MINIMUM SURFACE INTERVAL

As a consequence of Henry’s Law, while diving our body starts to accumulate nitrogen in the tissues due to the higher environmental pressure of the water.

While ascending, the body begins the desaturation process, releasing excess nitrogen so far dissolved in the tissues (so called “off-gasing”).

This process is not immediately completed when we reach the surface: according to DAN (Divers Alert Network) the off-gasing can be considered complete after a period of 12 to 24+ hours, in conformity with the type of diving activity (single recreational dive, multi-day / repetitive dives or demanding deco dives).

Nevertheless, in the diving industry it is a common and popular use to opt for repetitive dives: all of us have been diving at least two times per day during holiday, if not three or more, without particular problems. In fact, this is a safe practice if we respect the recommended surface intervals between the dives.

We can determine the minimum surface interval between two repetitive dives by calculating the Pressure Group and Residual Nitrogen Time with the help of more or less conservative dive tables (e.g. US NAVY) that generally consider surface intervals from 10 minutes to 12 hours.

But what is the recommendable minimum duration of a surface interval, and why?

Among other topics, a DAN research from the year 2017* (see fig. 1) has investigated, in a significant amount of volunteers, the trend of bubbles formation after surfacing, localizing a peak between 30 and 45 minutes after the dive. In other words, when surfacing even from a very simple recreational dive, we reach the maximum amount of bubbles in our body tissues between 30 and 45 minutes after the dive.

Fig. 1

 Thus, diving in this time interval is highly discouraged at least for two reasons:

• Synthoms of potential DCS usually are visible more likely 40 minutes after the dive, and we do not want to be in the water when they appear.

• Potential bubbles in our body tissues, during the second dive, are subject to uncontrolled recompression and this could lead to higher uncontrolled mobility within the body, thus resulting in serious pathologies. The more bubbles we have in the body, the higher is the risk of incurring in serious pathologies!

Considering the above, it is highly recommendable to wait at least 1 hour before a consecutive dive: in fact, only after one hour the amount of bubbles starts decreasing regularly. In any case only after 90 mins bubbles significantly reduce!

Note that this post just represents my personal opinion and does not have scientific value.

*Source: Cialoni D., Pieri M., Balestra C., Marroni A., Dive Risk Factors, Gas Bubble Formation, and Decompression Illness in Recreational SCUBA Diving: Analysis of DAN Europe DSL Data Base, Frontiers in Psychology.

PEEING IN YOUR WETSUIT

Even though many people consider it embarrassing, peeing in the wetsuit is completely natural and almost inevitable, as a consequence of the so called mammalian dive reflex and in particular of the Gauer-Henry reflex.

During the dive, mechanical factors such as absence of gravity (not 100% correct but let me put it this way), vasoconstriction due to temperature loss and increased environmental pressure trigger a substantial blood flow from the body extremities to our body core and thus towards our vital organs, giving them the false impression of a fluid overload.

The extra blood volume activates mechanoreceptors located in the surface of heart and lungs that transmit to the kidneys an order to produce urine, in an attempt to regain the fluid balance in the body.

As easy as that!

So, scientifically seen, peeing while diving is very natural because it is a survival mechanism!

Anyway, if peeing in the wetsuit is really unavoidable and socially accepted (among divers, at least...) for sure we can minimize its consequences, for the sakes of our dive buddies, with some simple rules:

• before the dive avoid diuretic beverages such as coffe, to reduce the urge. Anyhow, keep in mind that pre-dive hydration is essential to prevent DCS and the amount of water in your body plays only a secondary role in the diuresis process. On the contrary, a lack of water in your body will result in an stronger smell;

• buy your personal wetsuit as soon as possible, avoid peeing in rental suites. Do it for you, for the next customer and for who is going to clean the wetsuit after you used it, as a matter of respect;

• if you need to pee, do it early in the dive and not in the very end of it;

• during the dive open the neck of your wetsuit and let some water inside it before climbing back to the boat, it will help to reduce the smell;

• never hang the wetsuit upwind on the boat: if you do not smell it, this does not mean that also the other don’t!

• when you rinse the wetsuit do not put it in the same tank with other people, use the shower and rinse the wetsuit inside out with abundant neutral soap;

• remember that urine contains bacteria: clean the wetsuit inside-out, with neutral soap, and let it dry carefully before turning it over.

PLEASE DO NOT PEE:

• in your semi-dry!
• in your drysuit (unless it has a pee valve)!

 

 

POTENTIALLY HAZARDOUS MARINE LIFE AND SCUBA DIVING: THE MEDITERRANEAN SEA

A few weeks ago I was discussing with a friend whether it is a good idea or not to recommend divers not to wear gloves as a measure for the safeguard of the environment, psychologically pushing on the potential risk of injuries caused my marine life forms if touched bare hands.

This gave me the idea for a short research about potential hazards that can be caused by marine life forms, focusing in particular on the Mediterranean area.

My purpose here is to show you how limited is the risks for us scuba divers, if we follow two simple rules:

• do not touch anything (also with the help of some buoyancy practice);
• respect marine life forms without harassing them.

In fact, statistically the high majority of accidents and injuries from marine life forms are caused by negligence or fault of scuba divers that provoke the animals!

Basically it is possible to identify 3 large categories of wounds that can be inflicted by marine life forms:

1. Traumatic injuries (e.g. bites and punctures);
   
   
2. Stinging and envenomation, often in connection with bites or punctures. Envenomation is the process by which a venom or toxin is injected into another being and can be active (like in the case of jellyfish and some cone snails) or passive (scorpionfish, weever);
   
   
3. Electrical shock: some marine animals can produce electricity through particular organs for hunting and self-defence purposes. 

Let us now have a look ath the most "dangerous" animals of the Mediterranean Sea. As you can easily realize, the danger is more in our head than real!

📸 (c) Dario Romeodario 

@romeopix.com

Jellyfish: there are over 100 different species of jellyfish. The stinging cells, called nematochysts, are located on the tentacles. Only in some species the venom causes an adverse reaction in humans, with effects that range form mild discomfort to extreme pain, but some species can be deadly. The contact usually occurs accidentally, with the diver not being aware of the presence of the jellyfish. Wearing a protection suit drastically reduces the risk of being stung.

📸 (c) Frédric Ducarme

Echinoderms: to this family belong sea urchins and starfish. Seaurchins in particular represent a hazard if involutarly touched by divers with bad buoyancy. Most species in fact possess long, sharp, pointed spines that are brittle and break off easily in contact with human skin and in some cases can be venomous. Divers and snorkelers can be injured while swimming on the surface in very shallow waters as well as when entering or exiting the water from shore dives.

 
Fireworms: fireworms can be found in the whole Mediterranean Sea, expecially around the Italian coasts. It is a slow creature, easy to be spotted crawling on the sea bottom, and is not considered a threat to humans unless touched. Its bristles can penetrate human skin, injecting a neurotoxin that produces intense irritation and a painful burning sensation around the area of contact. The sting can also lead to nausea and dizziness. This sensation lasts up to a few hours.

📸 (c) Roberto Pillon

Weever: weever do not have a swim bladder and during the day they bury themselves in sand snatching their prays. They have venomous spines on their dorsal fin and gills. The vast majority of injuries occur to the foot and are the result of stepping on buried fish. If stung, significant pain begins about 2–3 minutes after being stung. Weever stings cause severe pain: common and minor symptoms include, among others, severe pain, itching, swelling, heat, redness, numbness, tingling, nausea, vomiting, joint aches, headaches.

📸 (c) Wilfried Berns / Tiermotive.de

Scorpionfish: are a family that includes many of the world's most venomous species. In the mediterranean sea the most common species is the red scorpionfish. Normally 30 cm long, its colour ranges from red to light pink, with dark coloured blotches on the body. It is a sedentary demersal fish that lives on rocky, sandy or muddy bottoms. The spines, located on the dorsal fin and next to the gills, cause a very painful sting that can lead to loss of consciousness.

📸 (c) Steven van Tendeloo

Moray eels: there are aproximatively 200 species of moray eels worldwide. Altough their apperance may look aggressive as they are often seen with their mouth open, this is just their way to breathe. Moray eels are night hunters and feed on small fishes, molluscs such as squids and cuttlefish and crabs. They are generally not a threat if not molested, so as a general reccomandation, avoid sticking your fingers in their open mouth! Their bite is not venomous but can lead to infection.

📸 (c) Robert Patzner - Fishbase

Barracuda: although great barracuda can be potentially dangerous as some attacks agains humans have been recorded, this species is not present in the Mediterranean Sea. Here the only common species is the Sphyraena Viridensis, that has generally a length of 35 - 40 cm, can be spotted swimming in large groups and it is not aggressive. 

📸 (c) Gargolla

Stingrays: stingrays have a flat shape and can be usually found in shallow, sandy areas. They may be buried partially in the sand, making them more difficult to see. They have a stinger located on the tail. The stingray’s reaction to pressure on the body (as when a diver steps or kneels on the animal) is to whip the tail up and erect the spine so that this motion inflicts a puncture or a laceration wound. The initial symptom is pain, which can be significant and intensifies over several hours. It is common for stingray wounds to become infected.

📸 (c) Philippe Guillame

Electric rays: the electric-shock producing organs are located on the wings and the fish stuns its prey by hovering over it. If a diver accidentally touches the electric organs can receive a similar shock that can be painful but very unlikely to cause loss of consciousness. Most incidents occur in limited visibility when a diver is crawling on a sandy bottom.

📸 (c) Patrick Doll

Triggerfish: triggerfish have a strong- jawed mouth with teeth adapted for crushing shells that can cause painful injuries. Males are territorial and fierce in guarding their territories, that extends in a cone from the nest toward the surface, so swimming upwards can put a diver further into the fish territory. A horizontal swim away from the nest site is best when confronted by an angry triggerfish.

📸 (c) Doug Costa, NOAA / SBNMS

Sharks: Mediterranean Sea is home to about 90 species of sharks, most of them not dangerous for humans. Among them, spiny dogfish is provided with spines that secrete a mild venom, located near the dorsal fins. This species is not aggressive and uses its spines only defensively when captured.

Finally, just a few words about two invasive species that recently came to the Mediterranean area from the Red Sea through the Suez Channel (so called Lesseptian migration).

📸 (c) S. Rothman

Feathery stinging hydroid: common in the Red Sea, this species of hydroid has been spotted in the Mediterranean since the 90s. Hydroids are relatives of the jellyfish and also have nematocysts that may cause a mild stinging sensation. A more extensive contact results in a burning sensation. Victims generally develop pinpoint lesions, blotchy red rash, blisters and raised itchy weals, which may last up to 10 days before fading.

📸 (c) Alexander Vasenin

Lionfish: lionfish are venomous fishes commonly found in tropical reefs. Native to the Indo-Pacific, this fish is one of the most infamous invasive species in the Mediterranean. Lionfish have needlelike spines located along the dorsal, pelvic and anal fins. Their punctures can be extremely painful and lead to rapid development of localized edema and subcutaneous bleeding. Nevertheless, Lionfish are by no means aggressive. These fish are generally docile, allowing divers to approach closely. In fact, most lionfish-related incidents occur as a result of careless handling by spearfishing.

PROTOCOLLO PER LO SVOGLIMENTO DELLE ATTIVITÀ SUBACQUEE PROFESSIONALI NEL RISPETTO DELLE MISURE ANTI CONTAGIO COVID-19

SIMSI releases the joint technical protocol about the operation of professional scuba diving activity in compliance with the COVID-19 infection reduction measures. The documentation has been already forwarded to the Italian Government: click here or on the picture below to read the full article (Italian language only).

A FEW (RELAXED) CONSIDERATIONS ABOUT FINS

Speaking about fins my first consideration is... before thinking about which fins style and shape better adapts to you, train on the development of proper kick techniques, learn how to maximize (but also control) propulsion while minimizing physical exertion and consequently air consuption, focus on trim and buoyancy. At this point, the shape of your fins will be just a secondary problem.

During our Open Water course we realized that there are basically two macro tipologies of scuba fins (here I am not even talking about light open heel fins to be used barefoot as I consider them snorkeling fins not suitable for scuba activity):

1. foot pocket fins;
2. open heel fins with strap, to be used with neoprene boots.

The first category can be worn also bare foot and may seem a good solution for hot tropical environments, also because they are generally lighter and easy to pack in the luggage. All of us did use them at least once in our life, in the swimming pool or by doing snorkeling.

Nevertheless, if you are seriously into scuba diving I suggest to leave this kind of fins to snorkelers and always go for open heel fins and neoprene boots. You will soon recognize the advantages of this solution:

1. the rubber sole of the boots offer extra stiffness to your kick, transmitting the energy in a more direct way to the blade, thus maximizing the propulsion;
2. boots seat better in the foot pocket, tightly secured by the strap, and you do not risk to lose the fins as it may happen with lighter foot pocket fins when you kick too hard;
3. boots protect your feet from excoriation caused by the contact of your bare foot with the rubber foot pocket;
4. neoprene boots can be used as normal shoes and offer protection while walking on the boat or on the shore;
5. boots guarantee extra thermal isolation.

One word about the strap: open heel fins are distributed with a large variety of straps. By choosing your fins, you are also choosing your strap: make sure that the strap is of the right size of your foot, opt for one piece rubber bands or better iron springs, avoid adjustable or expanding plastic clip buckles that are often fragile and soon or late will break as well as bungee cords that are more likely to wear out by the use in salt water.

Finally speaking about fin design, in the mega expanded universe of market offer it is possible to identify main 5 categories, based on the blade shape.

Paddle fins: generally optimized for flutter kick, they represent the simplest design and basically display a blade directly attached to the foot pocket. Most models are mono or bi-material (plastic + rubber). Paddle fins often have different inclinations between foot and blade for optimized kicking angle. Many bi-material blades are designed with two or more channels that funnel the water flow along the whole blade length, improving propulsion.

Jet fins: technical fins by definition, optimized for frog kick technique. With the exeption of very few models they are prevalently made out a single rubber mold (thus very heavy) and display vents on the blades that have the purpose of minimizing the mechanic resistance of the water in the kick loading phase.

Split fins: thought and designed to make flutter kick less exhausting, split fins offer the same propulsion of paddle fins but with less strain. Basically the split, when you kick, creates an open angle in the blade that causes a pressure disbalance which “sucks” the water along the whole blade length, minimizing the effort but keeping the propulsion constant. Basically useless if used with frog kick technique.

Hinge fins: Recent design concept, the blade is connected to the foot pocket by a hinge. Developed in aquadynamic flume, this fin has been thought to reduce stress and strain in the foot ankle while mantaining good propulsion. In my – personal – opinion this is more a marketing claim rather than real and concrete measurable advantage.

Force fins: niche product, designed to imitate the tail of marine animals, used with flutter kick they offer a very good propulsion. Very good fins for walking on the boat. Not performing with frog kick and ridiculously expensive.

📸 Stefano Festini

Now that we learned something about the market offer, it is time to choose the right fins. Here some food for thought:

• choose the fins according to your personal kicking technique: if you practice only flutter kick, jetfins will not be performing and as anticipated, split fins will be almost useless if you try to do an helicopter turn;
• consider the kind of exposure suit you will use: many drysuit divers prefer to use very heavy jetfins in order to balance the slightly positive buoyancy of their legs given by the drysuit. On the contrary, using heavy jetfins with a 2 mm shorty could lead to feet down or dropped knees trim;
• this leads to the next suggestion: always consider the weight of your fins and its impact on your buoyancy. You may find very similar fins models and shapes distributed by different brands with very different weights;
• remember that wearing the wrong fins causes more strain and possibly cramps, so it is worth to invest some time and trial dives to find the right fins.

Conclusions:

• always choose a combination of open heel fins + neoprene boots;
• learn different kick techniques and try different kinds of fins;
• fins play an essential role on your trim. Study your position and your weight; distribution, choose a fin that helps you mantaining an horizontal position.

If you still do not have clear ideas, I suggest to opt for the simplest bimaterial paddle style channel fin with high and stiff sidebars that you can find. This solution offers a good compromise between propulsion and comfort and allows very good control also in case of frog / back kick and helicopter turn.

One last word about freediving fins: although some scuba divers use them, I suggest to avoid long blade freediving fins. They are specialty fins, and their long flexible blade offers high propulsion and minimizes physical exertion only in combination with the proper kicking technique. Moreover in our OW course we learned that in the water we want to move as less as possible so manoeuvrability, and not propulsion, must be our primary focus. In fact, using freediving fins in bigger groups may result clumsy and their long blades could lift lots of sediments. Eventually, long blades use a lot of space on the boat and are most likely to damage by giant stride entry.

And you? Which fins do you use, and why?