Let me start by saying that I have been a certified diver since 1990. As a base layer a wetsuit would not be a great idea. Up here in VT (read cold water) I dive in a 5mm Farmer John type suit that is easy to get into, but if nature calls I have to take the WHOLE thing off. Not a good idea in the winter. If you were bugging out to a fixed bug out point that you have prepped it could come in handy if you were going to spear fish or have somereason to stand in cold water. This would probably be one of the last things I might grab on the way out the door.