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