A mimic octopus gliding along the sand bottom.  The mimic is so named because,

for example, it appears to copy the body shape of a flounder when swimming like this.

(TK 3, Lembeh Strait, Sulawesi, Indonesia)

mollusk; cephalopod; octopus; mimic octopus; Mollusca; Cephalopoda; Octopoda; Octopodidae; Thaumoctopus mimicus, South Pacific