Float is signed a bit like a tiny person lazing about on a float in a pool. Take your non-dominant hand and lay it flat with palm facing up, then form an inverted letter 'V' hand with your dominant and lay it flat on the float. With both hands together, undulate them up and down, simulating the waves in a pool or the ocean.
Teach your baby or toddler the float sign in preparation for an actual swimming excursion or party.
This is a useful sign to teach along with all the other swimming pool or beach vocabulary, to prepare your child for the actual experience so that they are equipped to sign what they would like to express.