Very easy to kill. Primitive bow takes 4 or 5 arrows. Instead if grinding narcotic, hunt down this and harvest their bodies. They give you something called bio toxin which is used as a narcotic. Cant make arrows out of it, but its surprisingly BETTER than normal narcotics

Basilasaurus is pretty much immune to these guys attacks.

Their bio toxin Better then narcotics , lure it to shore , shoot with arrow ot stab with spear

They drop about 13-14 bio toxin

While they are dangerous they are the greatest source of narcotics in the game. They give what’s called bio toxin and this will make torpor rise faster. If you want to kill them safely lure them to a raft and then crossbow them down. They are fairly weak so you won’t need many shots to slay them. Your greatest worry will be the sharks but if you can kite them into these guys you will find it works to your benefit.