Sea pigs are sea cucumbers that live in the deep sea. They walk around using their tube feet, and the antennae-looking structures at the top of their “heads” are actually other modified feet. They are deposit feeders, and their mouths are surrounded by tentacles that sift through mud and grab onto food. They like to gather around and feed on whale carcasses on the seafloor.
A way to tell sea cucumbers and sea hares apart is to look for the head. Sea cucumbers lack a distinct head, while sea hares (as do other slugs) have a head with sensory tentacles.