A Kaernk, also known as a Water Lurker, is hungry creature that dwells in water and and completely invisible to the naked eye, acting as a minor yet memorable antagonist from Amnesia: The Dark Descent.
What the Kaernk is is unspecified, as all that is known is that it comes from the same universe Alexander of Brennenburg does and appears to hunt the player while they reside in the shallow pools of Brennenburg. Once entering the water, the Kaernk shall chase the player, Daniel, and kill them once it reach you, eating your flesh.
Though it is invisible, it splashes loudly thanks to it being only located in water, making it very easy to locate it. The way to avoid the Kaernk is to get on a vantage point where it cannot reach (such as a floating crate), find a dismembered human body part, and throw it a far away distance possible, triggering the aquatic beast to retreat and chase it before gobbling it up.