A good way of looking for these things (mobile): sweep the border of the map and the ocean floor, using an ichthy to keep everything away. Once you find one, park your ichthy somewhere, then swim up to the depth limit of the mosa (you might have to test where it is though, be careful, mosas can swim up FAST). Being off the ichthy will catch its attention. Swimming up to the depth limit will cause it to Aggro off of you, so go back and forth with going to its depth limit, attracting it, and swimming back up to fill it with tranqs. The basic idea is attract, swim up, fill with tranqs, repeat. Hope this helps!
READ THIS FOR MAJOR MOBILE TAMING AND LOCATION TIPSWhen looking for a Mosa in ark mobile you need to run these two cave and farm the the Lava cave and the ice one these give crossbows and swimming gear then you get a dolphin (now what you have been waiting for) to find these with ease you need to kill the Plesiosaur and Leeds these actually clog up mosa spawns there mains spawns are behind herbi island and the artic ocean. The reason you farm the artifacts is they give you ascended gear so they last longer and the keep you warm ( I know this is not allowed but hit up so this goes out for mobile players because we need more help
(FOR ARK MOBILE PLAYERS) For my expierence i mostly encounter quite a lot of tuso, leed and many many megs, haven’t encounter a single one of that alpha, but when i encounter a mosa, it usually are an alpha, so i don’t thing tuso, meg and leed alpha exist in ark mobile
i hope this help you for ark mobile players, have a great play