Okay, first, some float, they are the ones that work. Some don't float, they are the ones that don't work, unless it's a submarine- but they shouldn't really be modelled c'cos you can't see them so whats the point in that...!
Second, some go fast and are meant to go slow, some go slow and are meant to go fast, some have propellors, some have jet engines, some have IC engines, some have steam engines.
Third, a lot are plastic (GRP), some are wooden and just a few clever sods have built some metal ones too.
Fourth, you need a sense of humour, a pond and boat and you will make many freinds on here.
Greg
PS- DickyD, as much as it pains me to say, is very knowlegeable, and I think what he means is that if you have any inclination towards any type of boat then let us know and we can point you in the right direction...