My DS8 had a great fear of the water at that age, and probably for about the same reasons -- we live on a river too, and so he had heard all about it for years. But he was (and is) a scaredy-cat about a lot of things when he's not familiar with them. We are planning on getting him swimming lessons this year, and he tells me that he doesn't want them and seems afraid, even though he likes to go to the rec center pool and work his way around the edges, holding on. We shall see how it goes.