Mertock is an antagonist in Treasure Planet and one of the alien pirates in John Silver's crew. He seems to be an anthropmorphic manatee with clawed fingers, coiled tentacles that serve as his two legs, and a pudgy horn-like limb that sprouts from his head. He had a part in the raid on the Benbow Inn, (yelling out "Where is it?!" scavenging through drawers containing silverware for the map that Billy Bones
tried to hide from the pirates. It is unknown what had happened to Mertock in the film, as he is last seen restraining Amelia when he, Silver, and the other pirates ambushed Jim.
Mertock with a lifeline
Pirates in the ship room
Turnbuckle, Crex, Mertock, Grewnge and Blinko sleeping with Silver