A rare mimic octopus.   This octopus can change color and shape readily.

It can also disappear into very tiny holes in the sand when it is not hunting. 

 (Gonabalabala, Milne Bay, Papua New Guinea)

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