Man-Eating Mollusks

The man-eating mollusks, or simply 'the Mollusks', are a herd of huge purple clams who appear in the season 5 special 'Pest of the West' after Patrick's great-great grand-uncle Patrick Revere warns the people of Bikini Bottom about them.

Description
Their shells are greyish-blue, with the shells being lighter on the inside and they have a big pink tongue. They swim quickly and act more agressively, when compared to their larger, calmer counterparts that we see through-out the series more often.