Popular Myths

Dive Suits

Myth: Wetsuits work by trapping a layer of water between your skin and the suit, which warms up
Fact: The insulating in a wetsuit is done by the gas trapped in bubbles in the neoprene. Water conducts heat very well. The less of it you get in your suit, the better!

Myth: Titanium linings add warmth to wetsuits
Fact: Those foil blankets you see at the end of marathons and packed in first aid kits increase warmth by trapping air and reflecting radiated heat. A wetsuit has no air in it, and looses heat via water flushing and conduction, not by radiation. No independent test has ever found titanium-lined neoprene to be better than normal neoprene.

Myth: Fleecy linings add warmth to wetsuits
Fact: Fleeces insulate you by trapping pockets of air. They do not work when wet. In fact, by allowing water to migrate through the suit, they increase flushing and can make you colder! Smooth linings that can seal against your skin are far more effective.

Myth: Inverting a drysuit leads to feet-first rapid ascents
Fact: The mere act of inverting a drysuit does not affect its buoyancy. If you were neutral to start with, you will remain neutral when upside down. If you get ballooning around your ankles that makes it hard to fin, you may well be over-weighted.

Myth: Neoprene drysuits are better because you'll stay warm if your suit floods
Fact: Since the advent of materials like Gore-tex and Pertex, which are breathable but waterproof, undersuits have been made which are largely unaffected by suit floods. Some, such as Weezle, even incorporate one-way wicking that ensures any water that does make it into the undersuit gets shoved straight back out again.

Myth: A flooded drysuit will drag you to the bottom!
Fact: Water in a drysuit is weightless whilst you're in the water. A suit flood may make it hard to get out of the water when you surface, but will not prevent you from making it back to the surface.

Dive Computers

Myth: Computers always give less deco stops than tables
Fact: On a square-profile dive, there's very little difference. Some computers also pad their deco estimates to add safety and protect the manufacturers – it’s not uncommon to end up doing more deco with computers than tables!

Myth: Computers are more versatile than tables
Fact: If the only tables you have are BSAC 88's, this is hard to argue. However, software is available (free!) that allows to you custom-make your own tables for all types of dives, at whatever level of conservatism you like: The BSAC Extended Range course teaches how to use them safely.

Myth: Computers are the most up-to-date way of calculating your deco
Fact: Most computers use Buhlmann’s algorithms or a derivative to calculate decompression. There is a growing body of evidence that suggests there are better ways of carrying out decompression, including slower ascent rates and deeper deco stops.

Myth: Only novices use tables, everyone else uses computers
Fact: Actually, many of the most advanced technical divers in the world use tables.

Myth: Computers can accurately modify deco requirements depending on conditions
Fact: Some computers can analyse ambient temperature, and will require more deco in cold water than warm. However, if you're snug and warm in 18 degree water in your drysuit, but shivering in your shorty at 28 degrees, your computer is going to be altering your deco in exactly the wrong way.

Myth: Computers know exactly what's happening to you during a dive
Fact: Computers know what is happening to them. They don't actually know anything about you. A computer will give the same deco requirements to a super-fit regular diver in top health as they will give a sumo-wrestler-look-alike who smokes thirty cigarettes a day and dives one week a year. Would you rather use a table that is exactly right for you, or a computer that is reasonably good for everyone?

Myth: That's why air-integrated computers are best! They DO know what you're doing!
Fact: Not really, they only know how fast your cylinder pressure is going down. A sudden drop in cylinder pressure could be down to a drop in temperature, inflating a drysuit or BCD, inflating a dSMB, suffering a freeflow, or breathing more. Nitrogen loading is a very complex process, affected by what gas you're breathing, how deep you are, how fit you are, and how hard you're working. Your breathing rate is not a good indication of how fast you're on-gassing: Being nervous can increase your breathing rate as much as hard work, but will lead to different on-gassing. And if you have to donate your octopus to your buddy in an emergency, do you really want your computer to make you do extra deco because it thinks you're breathing faster?

Myth: The best way to do a dive is to follow exactly what your computer tells you.
Fact: The best computer you have is the one between your ears.

Nitrox

Myth: Breathing air is the best gas for a scuba diver to use.
Fact: The less Nitrogen you breathe underwater, the better off you are. Adding Oxygen to air to make Nitrox is highly beneficial.

Myth: Nitrox is a deep-diving gas.
Fact: Nitrox is at its best around the 20-35m range.

Myth: Nitrox requires specialised equipment.
Fact: Nitrox requires you to have your cylinders cleaned. Unless you use very high Oxygen mixes to shorten your deco obligation, that’s all you’re likely to need. The only exception is certain regulators that cannot be used for Nitrox – primarily those that contain Titanium.

Myth: Nitrox, by having a lower level of Nitrogen in it, reduces narcosis.
Fact: This is actually still debated. Some divers claim to feel much less narked on Nitrox, whilst others say it makes no difference. Some studies show Oxygen to be narcotic, others do not. Try it and make up your own mind!

Myth: Nitrox makes you feel less tired after a dive because your body gets more Oxygen.
Fact: If elevated Oxygen alone made you feel less tired, going deeper for longer would make you feel less tired. Post-dive tiredness is actually believed to be due to sub-clinical DCI – bubbles that are too small to cause overt symptoms of Bends, but still put stress on your system. Nitrox cuts down on these bubbles, and so lowers the strain your body undergoes on a dive.

Myth: Nitrox is only of use to extreme divers, there’s no point in recreation divers using it.
Fact: BSAC tables give 20 minutes no-stop time at 30m on air. Alternatively, you could use Nitrox and have 32 minutes. If you want to reduce or completely avoid deco, Nitrox is very useful, especially on multiple-dive trips.

Myth: Nitrox fills are complex things that require dive shops to take ages and charge loads.
Fact: Nitrox blending is actually fairly simple, and this club will be able to offer it to its members at a very low cost as soon as the compressor is made ready!

Dominic Humphries

This page was last updated on : 06 Sep 2011