When they were very young they kept their heads way down and breathed through a tube that ran out near the tail-end of their bodies. This tube had a cluster of tiny wing-like things on the very tip, which kept it floating on the top of the water. They had no work to do, so they just ate food which they found in the water, and wiggled, and played tag, and whenever they were at all frightened they dived to the bottom and stayed there until they were out of breath. That was never very long.