Wet suits are by far the most popular form of exposure suit and therefore, the most well known. You can get them in many styles, patterns and thicknesses making them suitable for insulation in water as cold as 10 degrees Celsius and as warm as 30 degrees.
How do they work?
Wetsuits reduce heat loss by putting a layer of insulating foam neoprene over your skin. Wet suits get their name because you get wet while wearing one, water enters as the wrists, ankles and neck and gets trapped between your skin and the inside of the suit. Your body quickly heats the water and then as long as it remains trapped, you only lose the head as it radiates slowly through the wet suit material. If water circulates in and out of your suit, however, you lose a lot of heat to incoming cold water which is why it is very important to have a snug fit with tight wrist ankle and neck seals (though not uncomfortably tight, aim for a happy medium).
As mentioned earlier, wetsuits are available in a range of thicknesses, from 3mm up to 7mm making them a good choice if the water temperatures you will be diving in will vary. You can always add a body suit (see Body suits) under of over your wetsuit for extra insulation.
Wet suits are made from closed-cell neoprene foam lined on both sides by nylon or another material, for strength and appearance. Closed-cell means that the bubbles in the foam differ from sponge in that the bubbles don't connect. Neoprene won't soak up water like a sponge will, nor will water flow through it. It is these thousands of tiny closed-cells that make wet suits buoyant. If you've not tried it yet, even a partial wet suit has enough buoyancy to float you comfortably at the surface. Without addition weight in your BCD or on a weight belt, this makes it quiet difficult to get below the surface, see out weight system page for more on this.
The gas trapped in the neoprene foam bubbles provides excellent insulation, but as you descend they compress from water pressure. Consequently, a wet suit loses buoyancy the deeper you descend. You can compensate for reduced buoyancy by adding air to your BCD, see the BCD section for more on this. It is therefore important to consider the depth you will be diving to when choosing your wetsuit.
Selecting the right Wetsuit for you
When trying a wetsuit on, you want it to be skin tight but not too tight that it will restrict circulation and movement. You should also bear in mind that they will expand a little once in the water, which is why you should not buy one which is loose, you don't want water sloshing around inside the suit. It is meant to trap a thin layer of water but too much will impede on insulation efficiency.
You can get a lot of extra features with wetsuits such as lining, reinforced knee pads, wrist and ankle zips and pockets. These are all additional features which are down to personal preference. The main features to consider when choosing a wetsuit are, neck, wrist and ankle seals, and a snug fit.
Trying on wetsuits is hard work, and you will be tired after the second or third one so make sure you know what you are looking for. It is advisable to go for one with a zipper at the back as these are much easier for getting in and out of, as opposed to front zippers. Again, like most dive products, it is down to personal preference but most brands install the zip at the rear now as this is the preferred choice.
If you are going to be diving abroad or in warm tropical waters you might prefer the use of a short wetsuit also referred to as a 'Shorty'. These do not offer as much insulation, and as they are designed for warmer water, they often come in thinner neoprene ranging from 2-3mm.
Obviously, because your arms and legs are exposed, you are more vulnerable to cuts or scratches but this style is preferred by many divers who dive abroad in warmer water as it does offer more flexibility. This added flexibility means they are also great for other water activities such as surfing, snorkelling and jet skiing.