Gator

From the Super Mario Wiki

Gators are recurring enemies in the Wario series. They debut in the first Wario Land as members of the Brown Sugar Pirates, in which they wear inner tubes and lie in wait in a lake. When Wario crosses the lake, Gators leap up and snap at him.

They return in Wario Land 4, where they have traded in their inner tubes for a snorkel, but behave much the same. They only appear in a hidden room in the Monsoon Jungle.