We brought/will bring Coast Guard approved vests for the ocean for both kids and for my youngest in the pools. Noodles and I believe blow-up floaties or floats are not allowed. Puddle jumpers are coast guard approved, I believe.
Honestly, in the pools there is not enough room to "swim" so for older kids they will just be sitting, standing and splashing.
At CC there are snorkeling vests that are air inflated that are free (by the lifeguard stations), but it was too big for my three year old.
Perhaps five and above would be a better size?