Swim lessons may give me a heart attack

My kids are taking swimming lessons.  While Mia is cautious and careful, Paxton is wild and has no fear.   I am terrified whenever he is near the pool (including while he is taking swimming lessons).  He is quick to step off of the steps into the deeper water, has no fear of the diving board and jumping off, and wants no help.  Here are a few pictures. 

How do you keep your kids safe when they love the water and refuse to wear a life jacket?