Cipactli
In Aztec mythology, cipactli was a primeval sea monster, part crocodilian, part fish, and part toad or frog, with indefinite gender. Always hungry, every joint on its body was adorned with an extra mouth. The deity Tezcatlipoca sacrificed a foot when he used it as bait to draw the monster nearer. He and Quetzalcoatl created the earth from its body. This type of legend has roots in reality, because cipactli are ravenous. They have little or no regard for self-preservation; attacking prey many times their size. However, they seldom lose even such battles due to the size and the speed at which they can bite. With enormous mouths, they take huge chunks from their prey and can easily bite a human in half.
Cipactli are water creatures left over from the Age of Myths. In those ancient times, demons, gods, and spirits fought all over the Earth with magic and curses flowing freely across the lands and seas. Being around nine feet long and weighing hundreds of pounds, they resemble a hybrid between a piranha and a frog. Cipactli also have a thick skin and are quite durable against physical attacks. Not very streamlined, they are generally bulky and slow, but tenacious. Once they have prey in sight, either their victim or they will be the one to swim away.