Last summer my granddaughter took survival swimming from Infant Swimming Resource. I described our experience in my book, but you can see from watching the video clips at their site --- it can be scary for the both the child and the guardian. For more information visit their national website at http://www.infantswim.com/.
Once a year the child takes a refresher class for a week, or longer if needed. These lessons are just one way to protect children from drowning. Others include pool enclosures, out of reach door bolts and always, always, always knowing the whereabouts of your child, especially around water.