Water types aren't made of water. They are just animals that happen to thrive in water.
I wouldn't say they thrive in it, because some Pokemon can live in it, but don't or they use water in attacks, but are never in it. But yeah that first point is right, none of the water types is made of water. I'm not sure what rotom-w is about, but I'll just say it's watter.
Rocket Professor ~ R ~ Support Elesa! Real Arceus. Third Version M 2/26/13 Official ANBU of the Pokemon boards.