Part 8: A discussion on diving and air consumption: Trim

If you get yourself neutrally buoyant but find that you fall forwards, backwards or to one side or another then your trim needs adjusting (imagine everyone on a small plane suddenly standing up and all moving to one side!).

You can correct yourself in the water, (using movement, energy and therefore more air) as many times as you wish however you will always fall back unless you correct the cause.

The solution is normally as simple as shifting a weight slightly. It won’t fix itself - don’t put up with it!

Diving with Diabetes – an update

Following on from my previous blog item posted in February, the Undersea and Hyperbaric Medicine Society (UHMS) and the Divers Alert Network (DAN) have published consensus guidelines resulting from their 2005 co-sponsored workshop, ‘Diabetes and Recreational Diving: Guidelines for the future.

What was historically considered an absolute contraindication to diving is now being openly supported for those who are medically evaluated and who carefully monitor their condition and meet certain criteria. The view held by the medical community on people who have insulin-dependent diabetes was relaxed and those using dietary control for their diabetes should easily be able to meet the guidelines.

Note that the report has issued guidelines and not rules and should only be used as toll for the physician when evaluating a person with diabetes for diving.

The full ‘Diabetes and Recreational Diving: Guidelines for the Future’ can be ordered by contacting DAN Americaswww.diversalertnetwork.org

Part 7: A discussion on diving and air consumption: Buoyancy

Mastering your buoyancy is a key skill relevant to all aspects of your diving. If you have complete buoyancy control you can eliminate extraneous movements underwater.

As water is so dense, all movements use much more energy than the same movement on land and hence use more air. Correct buoyancy also allows you to perfect the fin kick of your choice to propel you most efficiently through the water.

There are many fun exercises you can do to hone your buoyancy but something you should do all the time on every dive is use fixed visual references to give you a continual picture of where you are relative to everything else.

If you catch buoyancy lapses quickly, you spend less energy correcting them thus conserving more air.

Rare "Prehistoric" Shark Photographed Alive

Flaring the gills that give the species its name, a frilled shark swims at Japan's Awashima Marine Park on Sunday, January 21, 2007. Sightings of living frilled sharks are rare, because the fish generally remain thousands of feet beneath the water's surface.


Spotted by a fisher on January 21, this 5.3-foot (160-centimeter) shark was transferred to the marine park, where it was placed in a seawater pool.

"We think it may have come to the surface because it was sick, or else it was weakened because it was in shallow waters," a park official told the Reuters news service. But the truth may never be known, since the "living fossil" died hours after it was caught.

See these photos and more at National Geographic

Part 6: A discussion on diving and air consumption: Weighting

Correct weighting is essential for efficient air consumption.

Weighting is a key component in buoyancy control (discussed below) but also has a tremendous impact on your efficiency in the water. Overweighting tends to drag the lower part of the body down so even if neutrally buoyant, divers need to kick continuously to remain horizontal in the water. All that kicking requires energy which requires air. To make matters worse, if you are over weighted, you will need to add more air to your jacket to remain neutrally buoyant at depth – your jacket will therefore have more volume causing more drag through the water. A double whammy on your air consumption!

Additionally, the more weight you carry, the more inertia you have (think about a truck braking as opposed to a car) meaning it takes more effort to change direction and as we know effort equals air – is there such a thing as a triple whammy? Under weighting will have similar impact on your air consumption as you struggle to kick down towards the end of a dive whilst your tank is trying to pull you up.

Remember you will breathe 1.5kg plus of air during your dive so always adjust your weight for the air you expect to have at the end. If you are correctly weighted for 1 dive are you necessarily correctly weighted for another (assuming no changes in wetsuit etc)? Not necessarily! If diving in current, which is frequently in Fiji, I find it easier to be slightly over weighted. You can use less energy if having to swim into a current by ‘falling’ into it using your extra weight.

Also if there are up currents you can use the weight to your advantage without having to swim down.

At any rate, think about the dive you are doing and weight accordingly.

More from the ‘Shark Trust’

A campaign has been launched to stop ‘Alibaba’ a Chinese online marketplace, from selling shark fins and other shark products. The decline of shark numbers worldwide is well documented. The ‘Shark Trust’ has gained enormous respect in scientific and political circles buy taking a stance calling for a sustainable shark fishery. Find out more about them at www.sharktrust.org .

The campaign to stop Alibaba is tackling the problem from the other end. There are more than 300 companies selling shark parts on Alibaba’s website – it is hoped that by making Alibaba aware of the vulnerable status of global shark populations they will agree to remove these companies from their site. Why should they listen? Alibaba is after a global market and already trades with over 200 countries and consumer opinion on its products may well affect its profits. As a result of a growing number of emails to the company, Alibaba has already agreed to look at the situation and talk with its suppliers. It is important that the pressure is maintained.

If you are at all concerned over the issues of shark finning, and the massive pressure on global shark populations through over fishing why not tell the company your concerns at www.alibaba.com/trade/servlet/page/help/contact_us_answer

Part 5: A discussion on diving and air consumption: Equipment

Again, as you learned in your dive course, equipment causes drag through the water, drag means extra effort which means higher air consumption. You learned therefore that the gear you carry should be streamlined.


What I am about to say may not be popular as many divers are very attached to their ‘gear’. Consider streamlining your gear by not taking it in the water in the first place or better still, leaving it at home! I can virtually put money on the guy who has been diving for years and is carrying half a dive shop underwater with him will be the first up. It’s always a matter of personal choice, but when diving in tropical waters you really can pare down to the bare essentials.

Why not take off your dry suit inflator hose – you won’t need it. It feels so much better when you’re not laden down with all the latest gadgets and it does wonders for your air consumption (and excess baggage charges!).

If you don’t have the ideal tropical setup, consider hiring you gear – your dive resort should have plenty of high quality equipment available for rental.