Here's a link that explains it somewhat:
http://allaboutfrogs.org/weird...
I also thought that toads are less likely to swim, living in damp, dark areas in gardens. But that being said, I certainly have a population of Southern Toads around my fish pond in the spring time. They don't hop in the water to get away when I get near them, though. They have a prolonged high-pitched whistle when they're mating, and usually the first big rain we get in May there will be a veritable rock concert of frogs and toads out there at the fish pond.
