Billybob, The drysuit comes in two types, Neoprene suits with built in silicone seals at the wrists and neck (the boots are built in), and membrane suits, which are waterproof nylon, also with silicone seals at wrists and neck. Underneath, you would usually wear a coverall suit of fleece or other insulating material. Usually, the diver stays nice and warm, (even if he gets a little damp). I dive in the North Sea, where the temperature ranges between 6c and 17c. As scuba is not a particularly energetic sport, (unless you're shore diving, and have a long walk to the water) its usually quite easy to maintain your temperature. I have simplified this a little as there are "dump valves" for getting rid of excess air from inside your suit, and an inflater valve to put some air in if you are getting "squeeze" from the water pressure. Once you have arranged this to your satisfaction, there is very little adjustment to be done. Anyway, thats how the suit works, so for the majority of the dive, all your body vapor stays sealed in there with you. So it tends to be beginners who are working hard that come out wet. I usually come out warm and dry, except for my cold fat lips, that were in direct contact with the water.
Sorry for wobbling on again.
I look forward to seeing what Fronkeys findings are
p.s. the wetsuit is neoprene but not sealed, and a thin layer of water lines the inside, to be warmed by your bodyheat. It isn't really an option for diving.