Sea pig

The Sea Pig is a sea creature in  introduced in the 1.3.0 Free Summer Update.

In
When donating to the museum, Blathers will say the following:

"Never have I seen a creature that walks the line between creepy and cute quite like the sea pig does. Sea pigs are, in fact, a type of sea cucumber that lives deep down on the ocean floor. About four inches long, these soft pinkish oddities use tube-like legs and feelers to get around. Thus they snuffle through the mud, slurping up particles from decaying carcasses. Meanwhile, predators be warned... This little piggy tastes like poison."

the sea pig is located in the deep water fish tank in the museum