Fourth Element Proteus. All you need. I dived with just a 3mm proteus and on most dives actually found it too hot! If the fit is right, the seals are so good the is very little water movement, once the water is inside, it heats up like a dream and stays there. Best suits on the market, and as someone else has pointed out, semi-dry is a made up, misleading term. Its either a wetsuit, or a dry suit. End of.