It does torpor over time while holding onto creatures. Although it does take a while to knock anything out on its own. Sharks and anglers will fall asleep in a few minutes but level 140 Mosa took 47 minutes for me. Would be better to have a tribemember to shoot it while you hold it.
Right analog is the ink/speed boost.
Left trigger is the torpor grab right trigger after for blood siphon heal and right trigger is regular attack. Tamed 10 takes a while to really get the hang of it left trigger them into walls ppl won't see them until its 2 late
You can grapple things and reverse drown them by forcing them out of the water, I've done this to an alpha megalodon, you can just take the items from their corpse once they're dead. Sometimes you've gotta push stuff up twice but it's pretty quick and efficient.