The King of Lakes

The King of Lakes (湖のヌシ) is a huge amphibious fish-like creature found in the largest lake in the 22nd Floor of Aincrad. It could only be encountered by using a special bait, which looked like a lizard, and required a very high fishing skill to lure the monster, while a very high strength skill to draw the monster out of the lake. It had the ability to swim as well as walk on land.

Aincrad Arc
Nishida, a well known professionally skilled fisherman, requested Kirito to help in catching the fish as he has the fishing skills to catch it but lacks the strength to pull the creature out of the water. Nishida got the fish and then «switched» with Kirito. Kirito managed to heave the thing out of the water but it turned out to be enormous. It started chasing Kirito, but was then killed by Asuna using her high level sword skill.