I agree, for swimming I think a child is better off, well, learning to swim.
We went sailing on a friend's boat for 4th of July and my daughter seemed quite comfortable in the vest. In the cockpit I just kept one hand on the handle at all times; she's young and impulsive and this was her first time sailing. My husband was a nervous wreck and didn't think holding onto the "handle" was enough, until I grabbed the handle, picked her up, swung her across the cockpit and dropped her in his lap. She thought it was just awesome.
It's extremely sturdy and is clearly designed to be able to haul a child out of the water. I'm very pleased with the construction.
I saw one other child on another boat wearing the same vest while we were at the docks. All the other kids I saw that day were wearing Type IIIs. I really felt secure with my choice. Thank you everyone for the buying advice.