We have four girls and so far our Maggie is the only one that really loves the pool.
Here is a video of her last winter when we were in Palm Desert swimming and fetching her ball.
I honestly wouldn't suggest a life jacket if you're right with them unless you're in a boat. I think it would restrict their natural ability to swim which they all have. All of my girls swim well but Maggie is the one that we just can't keep out of the pool.