Sea Snail

The Sea Snail is a rare creature that spawns in the Ocean on either end of the world, usually during the daytime and in a group. It slowly crawls along the sea floor. When killed it drops Purple Mucos, which is used to create Purple Dye at a Dye Vat. They are immune to the Confused debuff.

Triva
This enemy is like the snails in Spongebob that ate everyone, as they both look the same, have purple mucus and are in groups.

It also appears to be a reference to ancient Greece, where sea snails were harvested to make purple dye.