I'm against floatation devices because they create a false sense of safety and prevent the child from understanding how to float on their own, tread water, and most importantly, go under without panic. I am biased, having been a competitive swimmer from age 4, a lifeguard, and having taught swim lessons to some terribly scared children.
Even infants have natural abilities in water that go untapped if props are introduced, and the infants don't know fear, they just adapt to the water as humans have the ability to do. First time I saw that was in the 70s, it was the first child of an Olympic swimmer getting her kid in the pool with nothing. and he was doing great, figuring out how to move his arms and legs to get himself to Mom (Sharon Wichman Jones, Mexico City, 1968, Bronze for Breaststroke)
Better to teach them to swim and not need floatation devices. Children that tell someone they can swim when all they can really do is be supported by swimmies or styrofoam could be in trouble down the road.
just my opinion, having seen many dozens of infants in the water with no problems, and having seen and had to teach young-uns brought up the security blanket method. taking away the swimmies or whatnot can really bring on the panic and that is very difficult to remove.
It is, after all, the parents with the fear to start with, and then it passes to the kid in the form of Stuff They Can't Swim Without, says mom and dad.