When so many people are happy to swim in the sea virtually naked, why do divers need suits? Staying warm in the water must be the prime consideration. Getting cold during a dive can lead to breaks in concentration and mistakes being made and may even cause hypothermia.
Then there's the need for thermal protection during the sea journey to and from the dive site itself. It may be a long cold ride in an open boat, with no protection from the weather.
What about keeping skin, softened by long immersions in water, safe from abrasive surfaces like wrecks - or accidental contact with stinging hydroids or jellyfish? What about protecting skin from strong sunlight? And then, who doesn't want to look good? There's a bewildering range of garments sold for divers, ranging from thin diveskins to heavy drysuits. How, then, do you go about choosing a suit to meet your particular diving needs?.
Firstly, be aware that water is a great conductor of heat (it conducts heat about 25 times more efficiently than air).
There are few areas of the world where sea temperatures exceed human body temperatures. Assuming that you're immersed in water which is at a lower temperature than your body (around 37°C), heat will be conducted away from you, and you will eventually feel cold.
You may see holiday divers wearing nothing but swimming costumes, but their dives rarely last long. Unnecessary heat loss means more air used and shorter dive times.
Having said that, heated swimming pools and the warmest tropical waters may merit only the skimpiest of Lycra suits, especially if you have a moderate layer of epidermal fat. Some of these 'dive skins' now have hi-tech thermal linings to give them the insulation qualities of the thinnest neoprene. Remember, however, that they all have one property very much in common - if you're not happy with how you look in the nude, you'll only be setting yourself up for ridicule if you wear one of these. Those with bodies like a 1960s beanbag couch or a bag full of spanners need not apply.
Personally, I prefer to use a lightweight neoprene wetsuit (2 or 3mm) under these circumstances. Equipment straps on without chafing, and I feel a lot better about myself. From my observations at popular Caribbean resorts, I can't say that many burger-guzzling American divers feel the same way.
Since you lose the majority of your body heat through your head, you ought to start by wearing a hood. In practice, this is the last part a diver will cover, mainly due to the restriction of head movement, and the impairment of hearing caused by covering the ears. Lightweight neoprene wetsuits in shortie styles are popular for pool activities, followed by longjohns and longjohns combined with jackets. Then there are the one-piece combies which cover all. These usually zip up at the back.
These suits are available in different thicknesses - often 3, 5, 7 and 8mm. The heavier suits usually have hoods attached. The thicker they are, the warmer they tend to be; but more thickness means more positive buoyancy, and the more compensating weights a diver needs to wear.
The insulation comes from the tiny cells formed by blowing nitrogen through the neoprene when it's made. Unfortunately, these tiny integral bubbles of gas get compressed under the increasing pressure of the water that a diver encounters with depth. The buoyancy (and insulation) of the suit is consequently decreased as the diver goes deeper, and air has to be added to the buoyancy compensator (BC).
Wetsuits work additionally by trapping a layer of water between the suit material and the skin. This is warmed up by the body and adds a secondary insulating layer. If the suit doesn't fit properly, water will flush in and out, cooling the body and negating the effect of the neoprene. If a wetsuit is to work, it must be a neat fit.
Many diving instructors advise their trainees to buy suits which fit like a second skin. This, perhaps, is merely a ploy to stop them asking difficult questions during training, since they become totally exhausted from just struggling into the rubberwear. Such badly guided trainees always travel with a plentiful supply of talcum powder.
Semi-dry suits became very popular because, by using tight seals of smoothskin neoprene at wrists and ankles to discourage that cold flushing effect, they avoid the necessity for so precise a fit as ordinary wetsuits.
Semi-dry suits are very effective at keeping a diver warm under water. If you have a longjohn and a jacket you gain the versatility of using either or both according to the prevailing conditions. The one-piece combi-style suits also usually come with a waistcoat-like additional layer for adding to the torso if needed.
Italian suit makers have always given a lot of attention to semi-dry suit design, and two have recently come up with a revolutionary advance using more effective yet easier to don latex seals and even drysuit-style zips to minimise the amount of water that can enter.
The Italian suits look good, and make the wearer feel good about wearing them. Added to that, they also use a metal titanium fleck in the inner lining to add a further thermal barrier. This means that a suit can be made of a less heavy material for the same insulation values.
Suits like this are excellent for keeping a diver warm when he is actually in the water. However, anyone who has had the experience of getting back into a cold wetsuit for a second or third dive, especially at sea when it's breezy, or at an inland site in winter, will know what misery it can be.
Drysuits, by contrast, are designed to keep the diver dry, which might not be so important during the dive, but is particularly relevant afterwards. Remember James Bond in You Only Live Twice? He got out of his drysuit immaculately dressed in a dinner jacket. There's a feeling of self satisfaction which any diver feels when he steps from his suit still wearing the ordinary clothes in which he turned up to the dive site.
In the past it was easy to classify drysuits. They came in two types. One, the membrane drysuit, had all the style and charisma of a dustbin liner, and the other, the neoprene drysuit, left the wearer with all the mobility of Wurzel Gummage at his post, and probably wet arms into the bargain.
Membrane suits alone didn't keep you warm, however. That was all down to what you wore underneath. Neoprene suits had inherent insulation properties, but suffered dramatic buoyancy changes as you went deeper. This meant that you started off wearing inordinate amounts of lead and then, during the dive, had to compensate with similarly large amounts of air added to your suit and probably to your BC too. Now all that has changed.
New tri-laminate materials combined with modern bonding systems allow membrane suits to be made from more than the minimum number of panels, leading to better tailoring and a more flattering look. Tri-laminate and all-rubber suits invariably come with latex seals. The all-rubber membrane suit has, however, now almost disappeared from the leisure market.
Other membrane suit manufacturers opt to use neoprene for its resilience to hard use, crushing the bubbles out of it, or using modern American compressed neoprene, which causes fewer buoyancy problems. Often, thinner materials are used for better mobility, and at the same time undersuits are favoured as a method of retaining body heat. Modern bonding techniques combined with accurate cutting, in some cases by computerised machinery, allow neoprene suits to fit accurately.
Drysuit manufacturers vary in scale from the one-man-and-a-pot-of-glue setup to giant international corporations more famous for their car tyres and expensive wellies. However, since the process of making a drysuit is very labour intensive, this matters little. Only the quality of the final product is important.
It's important to distinguish between suits made from compressed neoprene, and those made from crushed neoprene, although both materials work in the same way. Compressed neoprene is compressed to reduce the inherent bubble size in the material at the point of manufacture, before it is supplied on rolls to the suit maker. Nowadays, compressed neoprene as thin as 2mm is used in drysuits.
Crushed neoprene is crushed after the suit is made. The suit is put (without hard parts such as valves) into a pressure chamber and the material is crushed, tightening up the bonding and stitching as well during the process. Because there is some distortion of the suit, it's hard to get a crushed neoprene suit made accurately to measure. They have a fearsome reputation for their hard wearing characteristics.
Neoprene suits usually come with a choice of neoprene or latex seals at the neck and wrists. Neoprene seals are hard wearing but, being relatively thick, may not be totally effective in preventing leakage in areas such as bony wrists, where body contours change abruptly. Neoprene neck seals need to be turned in like an inverted polo neck and then sufficient air added to the suit to maintain a little positive pressure.
Latex seals are thin but very elastic and consequently tend to keep the water out better. Because they are glued on, they can easily be replaced by the user if they get damaged. Tri-laminate materials are generally a layer of butyl rubber sandwiched under pressure between two layers of hard-wearing synthetic material.
If a suit leaks other than at the point where skin meets seal, it's almost always at a seam. All manufacturers therefore go to extreme lengths to make seams watertight, stitching, glueing and taping over the joins - even vulcanising in some cases. Seam technology has been important to the advancement of modern drysuit design. The designers of bad old dustbin-liner drysuits avoided seams at all costs!
There was a time when only one manufacturer could legally supply a drysuit with the necessary valves already in place. It was to do with patents. Proud owners of new suits had to take a scalpel to them and cut their own holes, often with less-than-perfect results. Today, most suits can be provided with the valves already fitted.
The input valve of a drysuit is normally mounted on the chest, but often you can ask to have it fitted somewhere more personally convenient. The same goes for dump valves. Usually a cuff dump is fitted or an automatic constant volume valve is fitted at the shoulder. The latter is more expensive, but has gained popularity.
Why do you need valves? Because a drysuit naturally contains air. As you go deeper, this air is compressed - causing a loss of buoyancy and possible discomfort as the creases that form in the suit are squeezed on to tender parts of your body. The inlet valve allows you to pass air via a direct feed from your regulator first stage into the suit to compensate for the compression of the suit's air space.
As you ascend at the end of the dive, this air will expand and, just as with a BC, you must let it escape if you are to avoid an ever accelerating trip to the surface. New drysuit divers have been known to forget to 'drive' their suits in this way and, trying to fin downwards as they gradually become more buoyant, end up with all the air in the legs of their suit, arriving unceremoniously at the surface, feet first, with their fins popped off.
Automatic dumps work by using a constant-volume valve principle. They only release air if the air in the suit exceeds a user's predetermined suit volume setting.
Air will always go to the highest point, so cuff dumps are also easy to use because you just raise the appropriate arm to make it the highest point. However, they're not so good for anyone who must raise an arm for any other reason during the dive (for example, a photographer reaching up to hold his camera above him), because all the air will automatically empty out. An automatic constant volume dump valve, positioned at the shoulder, works admirably - but users must be sure to position it at the highest point by raising that shoulder and rotating the upper arm during the ascent if need be. Care must be taken not to be overweighted, because if you need to put large amounts of air into your suit the auto-dump might not be able to release it quickly enough during an under-cautious ascent to prevent total loss of control.
The direct feed to a drysuit more or less makes the direct feed to your BC redundant. However, a BC is essential for additional surface buoyancy and in the event of failure of the air tightness of the suit. It can also be used by a diver to right himself should he find himself inverted with all the air in the suit migrated into the legs.
How do you get into and out of your drysuit?
They invariably use a heavy duty waterprooof zip which must be maintained in working condition with wax lubricant. These zips are traditionally positioned across the shoulders so that the wearer steps into the suit, puts his arms through the sleeves, then forces his head through the neck seal (often with the aid of some lubricant such as talc or baby lotion). Then he needs the help of his buddy to close the zip.
Some self-donning styles have met with acceptance among divers. These use a long diagonal front zip. After stepping up to the waist, often with the weight of the suit supported by integral braces, the wearer reaches back behind him to pull the suit over his head, which then passes through the neck seal. This is not always convenient for those with less than total upper body mobility. Then again, because some zips pass well over the left shoulder, wearers often have to ask for help in getting them started, defeating the purpose of the self-donning design.
Some suits add additional length in the body tube to simplify this manoeuvre of pulling the suit from the back, over the head. This then forms a tuck which is held in place by a crotch strap. Other suits do without either or both. Again, there are patents involved. When it comes to footwear, some drysuits merely have a pair of wellies added to the end of the legs. Others have purpose-made neoprene boots, with only a pair of ordinary socks needed for use with them. Either way, the footwear must be substantial because it meets the hard and sometimes sharp surfaces found on boats, at rocky dive sites, or, indeed, in carparks.
With the virtual demise of the standard 8mm thick neoprene drysuit, all suits need to be worn with some sort of undergarment, often called a woolly bear. It used be thought that these garments should be made of an open-weave material so that air never became trapped within the suit. However, the effect was rather draughty when wearing only one's woolly bear, without the drysuit, between dives.
'Thinsulates' and undergarments coated with Teflon-type materials don't allow the wind to blow through. Neither should the ordinary sweaters and jeans that you might also wear, in addition, under a drysuit. None of the above seem to lead to the trapped-air problems.
The new style undersuits come in a variety of thicknesses or tog-values, and it's down to the user to pick what's appropriate for the prevailing conditions. The latest have open-weave material around the forearms. This development was in response to a number of divers who experienced difficulties using cuff dumps when the smooth Teflon-type outer lining of their undersuits allegedly jammed against the internal face of their dump valves.
What about hoods? Well, years ago the Viking rubber membrane suit came with a dry hood which was extremely warm and comfortable. You can still get this suit, but its UK importers are now not very active in the leisure market. However, many divers experienced problems with reversed ear syndrome when ascending with dry hoods. Now, most drysuit manufacturers supply a thick wetsuit hood for use with their drysuits.
If you experience trouble with the pointed-head effect caused by exhaled air becoming trapped inside your hood, look out for those available with a simple flap-valve designed into the lining.
So which type of diving suit is best for you?
If you're a club diver not intending to dive outside branch activities, you might be well advised to bite the bullet and pay out for a good drysuit from the beginning. If you're only going to dive round the British Isles this is the type of suit you'll need. You might want to buy a lightweight undersuit, as an alternative, later. But if you use a thick undersuit, I can promise that you'll never be too warm in the water.
A thick semi-dry is often the choice of new divers, on economic grounds. It will keep you almost as warm in the water and has the advantage of offering better mobility. Cold RIB rides, however, can be numbingly uncomfortable. Be sure to carry a wind-proof garment to wear over your wet diving suit to avoid wind-chill effect. If you're on a hard boat, it's a good idea to get out of your wet gear between dives.
With unfamiliar locations, the best rule is to find out what the local dive guide will be wearing. They usually get it right! Naturally, some people have more natural thermal insulation than others. A 7-stone male diver will probably need a thicker suit than a 20-stone female! Our chart is recommendations based on our own experiences.