The Ugjuknarpak is a gigantic(human-sized) predatory aquatic rodent from Inuit mythology. It lives under the ice and overturns kayaks and other small boats. In addition, this beast has tough skin that is very difficult to penetrate and it also has a long prehensile tail to grab its victims and drown them underwater.
It may seem impossible for a rodent that size but it could happen, for example, 3 million years ago during Pliocene and ealry Pleistocene a rodent called Josephoartigasia monesi roamed South America and was the size of an African Buffalo. It is the largest rodent known.