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.