Selkie

Selkies look like a human-seal hybrid, and in fact their genetics are aquanaut with heavy splices of seal traits. Their arms are standard human-shaped, but their legs are fused into a pair of hind flippers for powerful swimming. On land, they can stand but have difficulty moving, as they must flop, roll, or hop like a seal. They are adapted for the lack of air, deep cold, and crushing pressure of subcrustal seas.