Swamola

Swamola is an enemy from The Legend of Zelda: A Link to the Past.

Swamolas are found exclusively in the Swamp of Evil in the Dark World. Their dark green bodies camoflague them well in the swamp, and they have pronounced mandibles. They do very significant damage to Link if they hit him, perhaps because of them. They hide under the water and muck of the swamp, lunging out of it to attack.

Swamola are immune to most of Link's weapons, and even require many hits from the sword to defeat However, they aren't aggressive and usually aren't dangerous to Link unless they surface near him.

Etymology
Swamolas are related to the Lanmola. Their name is even a portmanteau of "swamp" and "lanmola". This is directly stated in the official A Link to the Past strategy guide.