My ds has been swimming since he was an infant. We taught him ourselves at home without any fear or tears, it was always a happy game and we took our cues from him. The upside is that by about 16 months he had a good chance of saving himself if he fell in and was within 10 feet of the edge of the pool, the downside is that he has no fear. Though he knows the appropriate time/place/clothing/Mama is watching..etc... for swimming and respects those rules 99% of the time, he still has the impulse control of a toddler and therefore must be watched at all times. He probably could have been even better sooner, but we were not interested in forcing him. We haven't been swimming in a few months due to cold weather, but at the end of last summer he was about 25 months old and could easily jump/dive/slide in, swim the length of the pool, dive for objects under the water, etc.