Look I'm not a fan either, but my two are bolters and despite constant supervision, there's always that split second. Ours can both swim, but I wanted something extra for DS for when I had to tend to DD and he got away.
We tried the vest but I didn't like them as he could flip himself onto his face anyway. The bubble did the same thing but in reverse. We found a set of floaties that have a chest piece so he can't tip himself forward in the water should he fall in. He started with them at 16months old.