When my kids were small we had a little vest with a sewn-in intertube around the belly. It wasn't a vest like a life preserver, but a fabric suit that you slipped over the head like a shirt with armholes. They could "swim" all over the pool and stayed upright easily. Of course, it never takes the place of an adult in the pool with them!

I just did a quick search and found this one which was similar to the one we had. Scroll down a little ways on the page. It is called POOLMASTER Learn to Swim Inner Tube Trainer.

http://www.poolcenter.com/pooltoys_c...mming_aids.htm