Easy tame on genesis 2. Build 2 behemoth gates and block off a small section in the Crossway between the middle and NE quadrant. Leuer them in, shut the gate behind them. May need a good shark or something to fight off any thing else that follows you in. Should work for plesio and tusso too

Easy tame if you use a Behemoth Gate trap, place four gates down and one door on each end, leave enough space you can swim through with an Ichthy, have one door on the gates at either end, leave one closed, get it’s aggro on lure it in, swim around behind it & shut the door. Tranq and kibble. Easy Mosa.

in ark mobile just kill it and grab it's implant make a revival platform put revival platform in the water under the red oblisk revive it there you go it will not move since it has a depth limit sometimes it might try to swim away from you and it stops since it has a depth limit it's easier to tame and much more expensive to revive lol

Ok here’s what you gotta do. First tame a turtle and name it sacrifice then cryo that guy and find a tuso then tame a tuso. Ok so with the tuso grab the mosa and bring it to the surface. At a certain point near the surface it will completely stop moving and if it does it will only move down. Also when carrying the mosa with a tuso the mosa will attack it unless you bring it above where it is supposed to be so just swim up with it and it will eventually stop attacking. Up if you want idc

Bring an Itchyosaurus with you since they're pretty fast and things won't aggro it (at least on Mobile idk about PC/Console). Have a LOT of tranq/toxicant arrows, and search for your Mosa. When you find one, shoot it and let it follow you up to the surface.

Mosasaurs have a certain depth they need to be so they'll stop aggro when you reach a certain depth (near surface) and go ham with your special sleepy time ammo.

Make sure to watch its HP and Torpor so ALWAYS BRING A TELESCOPE WHEN TAMING ANYTHING! Don't kill the poor guy.

Give it some soothing balm if you can and feed it some prime fish and so on, use BIO Toxin to keep it asleep (you can get some from Cnardias probably nearby). Boom! You've got the Giga of the sea.. Sorta.

Hope this helps and good luck!

First to tame it you will need to get your scuba gear and a lot of tranqs to knock it out next you will need to find one you can find one on the edge of the map border and you can find them at the bottom where you find Pleids and dunks make sure to kill the pliers or dunks for a chance for it to spawn there and once you find a miss you can trap it with the rocks around it or use a fast water tame to get away and fire your tranqs to knock it out and feed it meat (prim meat works the best)and feed it loads of narcotics and meat and you have tamed a mosa also if you don’t keep them fed they will gain a lot of torpor and go into a coma for a while so KEEP THEM FED

This is more of a question but a level 14 one spawned near herbivore island where I live but it wrecked me and my level 40 basilosaurus. I saw tips saying I should get it to follow me and there are ammonites down there but that agros everything. I can’t afford to miss a shot though.