Here is a video I posted of my two swimming wearing the life jackets.... As you can see they are not very fond of the idea of being in the pool....
YouTube - ‪Swimming‬‏
I agree that the life jackets are very thin. My two weight 5 and 6 pounds. Its hard to tell if the life jacket actually helps or not. I may do a little experimentation with some five pound objects lying around and see what happens when they are wrapped in the jacket.