Honestly, all you have to do is repeatedly shoot at it with tranq arrows from a rock or something. i’ve discovered they’re easy to shoot because they’re so long and big, and not good climbers. of course, slow on land too. if it’s a low level you need under ten tranq arrows, but ofc if it’s higher i’d refer to more experienced players. just got my first one, super fast underwater for sure. hope this helps <3