Being too cold is never a nice thing, and neither is being too hot. In fact being on either side of the ideal temperature can actually be very dangerous and if exposed to the cold or to heat can actually kill you! We have all felt these temperature extremes at some point in our lives. It’s easy above the water, all you need to do is put a coat on or take a layer off, however it is a different story underwater.
You cool much quicker in the water than you do in the air, in fact you lose heat between 20 to 25 times quicker in the water. That’s why when you are on the beach in 22 degrees weather it might feel hot, but when you try to get into the sea which may be around 17 degrees, it is difficult to even get past your knees! The temperature change is not that much, but water makes it feel a lot colder.
Our body temperature should be between 37 and 38 degrees Celsius, and this is constantly being cooled by our surroundings (or warmed depending on where you are). The air is not so efficient at cooling us down, however water is very efficient. Our skin which is warm comes into contact with cooler water, which starts to cool the skin down which in turn slightly warms the surrounding water, however water molecules are constantly on the move, which means new colder water then comes into contact with your skin and the process continues. Our body can only take this constant cooling for so long before it becomes too uncomfortable, and eventually it will lead to hypothermia. A dangerous condition which can lead to body systems failing, confusion, drowsiness and if left untreated eventually unconsciousness and death.
This is why it is so important to keep wrapped up by having the proper thermal exposure whilst diving. There are many different types of thermal exposure on offer and they are used for different.
Wetsuit: The wetsuit comes in 2 basic styles, full length or shortie. They are made from neoprene which is a flexible, slightly stretchy and water resistant material (not water proof). You can get them in varying thicknesses which will depend on where you are diving. Usually they are 7.5 mm at thickest and can go down as low as 0.5mm although this thickness would not normally be regarded as a wetsuit. You often see different thicknesses in different areas too, normally thicker on the chest than on the arms and legs. This is because most of your vital organs are in this area and need more protection, and also because the thicker the suit the less you can move, so it may be beneficial to reduce thickness on arms and legs to increase mobility.Wetsuits allow a small amount of water through them, hence the name wetsuit. This means at first when you get in you will feel the chill a little bit. But a proper fitting wetsuit shouldn’t allow any or very little water movement, so your body will warm up that small amount of water inside the suit to around body temperature, keeping you nice and warm! If the wetsuit is loose fitting in some areas it will not work properly, as it will allow the water to move around inside the suit and allow cold water to enter the suit, offering you much less thermal exposure than it should do.
Semi Dry-Suit: The Semi Dry-Suit works in the same way as the wetsuit, it is also made from Neoprene and again comes in different thicknesses. The difference is that they have rubber seals around the arms and legs, to create a better seal than the wetsuit does to help prevent water from moving in and out of them, again they need to be properly fitted so the seals are tight, however as the water cannot move in and out as easily then can be a little baggier in other places which allows you more maneuverability. Especially liked by technical divers as they need full mobility of their arms to be able to reach behind them and shut down and open valves.
Dry-Suit: The ultimate in thermal exposure, a dry-suit will allow you to dive in the coldest of waters. You should use a dry-suit in waters cooler than 15 degrees Celsius. The main part of the dry suit is made a membrane type material, neoprene or foam rubber, or a combination. They also have a water proof zipper, which was originally designed by NASA as way to hold air inside an astronaut’s space suits. The zipper is usually the most expensive part of the suit. Again like a Semi Dry-suit, there are also rubber seals at the wrists, ankles and also the neck, to prevent water from entering. A dry-suit diver will usually find some moisture after the dive, even if the suit is completely watertight, from sweating and condensation. You find than many modern Dry-suit also have boots attached, so you can keep your feet warm during a dive too! Depending on where you are diving you may also need to wear an undergarment to allow for further thermal protection. The dry-suit is different from the wetsuit and semi dry-suit, as it is not an insulating layer of water that keeps you warm, but instead a layer of air, hence the name dry-suit. This makes diving a little more complicated, as you know air expands during ascent and compresses during decent, which means we need to add air to our dry-suit not only for buoyancy but also so we do not get a body ‘Squeeze’ suit compresses to our body. Dry-suits will always have a low pressure connection just like on your BCD, to allow you to connect another LPI hose from your regulator to the dry-suit allowing you to add air to it. They will also have valves just like your BCD (again) to allow you to release the air as you start ascending. If you are diving in a dry-suit you will normally use the suit itself as a way of controlling buoyancy, and ignore the BCD until at the surface. This is because it is easier to control one buoyancy device than it is to control two. Although this is not the case for technical divers.
Before diving in a dry-suit you should at least get an orientation into using them, or even better is to take a full course as there can be complications when using them, and you should know how to handle any issues should they arise. One of the biggest hazards of any type of exposure suit is over exposure to the heat. Putting on the suit too early with a long boat ride ahead in the sun can easily give a diver heat exhaustion or even heat stroke, again a condition that requires medical attention. To prevent this you should only put the suit on just before you need to gear up. I see lots of divers wearing their suits half way and sitting down in them, and this is just an easy way to rip where the zip is attached at the bottom.
One final tip is try not to pee in your suit… Although many other water sport enthusiast say its fine remember you are not moving around as much as a surfer or wake-boarder is, and the suit is designed to keep whatever liquid is in the suit, in. After a 45 minutes dive soaking in your own urine, you will smell. And everyone on the boat will know who did it. Trust me!
‘Keep wrapped up!’ was written by Mike
Photo Credit: ‘The Scuba Tank‘