Tank likes to swim on his own terms. He jumped in our pond and swam around in a cirlce and right back out when he was hot (he smelled like pond afterwards...yuck!) and he swims in our neighbor's pool. He'll come right to me but doesn't understand to swim back to the stairs when he wasnt out. Instead he swims to the wall like he's going to magically float to the top. I make sure to watch them and I wouldn't ever let them swim without me around, but Tank loves it!
Buckeye by Boston terrier on the other hand doesn't think much of water. He's like a motor boat in the wat ther though and splashed hard when he swims. I had them at the pool the other day while I was swimming laps and turned around to see Buckeye chasing me down the length of the pool like he was going to rescue me
Once he realized that I was fine he didn't want in again.