The trick to ko these guys is to wait for them to agro you, once they're close enough, swim up and backwards until you've reached their swim limit and shoot them as many times as possible. When they lose interest, just do the same trick and eventually you'll knock it out
These guys are great and super fast and also very strong. Warning when your gonna go tame these guys bring a sarco or an icthy , they also spawn In 2,s or 3,s so be careful because these guys do a crap ton of damage .
They can't fit through the resource caves' entrances. Just lure it into one and pull out your crossbow/harpoon gun for the knock out. Just be aware of any nearby megalodons, as they can fit into the cave easily and ruin your swimming session.