Today I 'bought' a new shirt of Tiki which is made of Neoprene, which has to keep me warm in the winter when I'm surfing. I also got me some 'internal heating things' which you can attach to that shirt. First you have to put that heating thingy in warm water so that it gets warmed up, then put it on your shirt and wear it under your wet-suit. It really keeps your body warm, and I'm able to surf longer now in the winter.
If anybody wants to know what it looks like, just tell me and I'll take some pictures of it. (Unfortunately I can't do that now cause I'm not even close to the shirt and internal heating.
Have fun with surfing!!!