They are literally prehistoric giant turtles. Like snapping turtles, but bigger. If you want to kill, then just get on a rock and shoot it, or, if you really like to be in danger, then go down there and put up a good fight. If you’re escaping them, DO NOT, DO NOT, DO NOT go in water. They are slow, but they have no oxygen so when you’re hiding in water, tough luck, idiots. You’ll die if you’re coming up for air.
This is an awful animal to underestimate. When I first played the game, I thought I could kill one for easy meat and resources. The douche took 6 spears to the face, broke my leg, and speed-walked after me as I limped away. DO NOT UNDERESTIMATE.