Every dog that I've ever owned as been able to swim, as from my understanding that's just a natural ability or instinct that they are born with. That doesn't necessarily mean that they all like the water though and while most if the dogs I've owned have, there as been a couple that wouldn't go near.
Some owners try and train their dogs to go into water as puppies, a bit like we do to our children when they're at an early age, but I'm not sure that I agree with doing that. Try them with water a few times, but if they don't like it I certainly wouldn't force them to go in, as that's bordering on cruelty. We can justify teaching our children to swim, and getting them used to water even if they don't like it because one day it might save their lives, but with animals it's totally different as they obviously won't understand.