Great all around underwater. Powerful and tanky. I have noticed they are able to survive a jelly fish swarm. I have mine kill around 40 jelly fish while being shocked.

I recommend pumping health and melee.

DO NOT CRYO POD WITH STUFF ON THE PLATFORM SADDLE, IT DESTROYS EVERYTHING. IT ALSO HAPPENS WITH OTHER PLATFORM SADDLES.

If you have 300+ oxygen they are relatively easy. Take advantage of their bad turn radius and stick close to their tail to KO.

DONT FIGHT JELLYFISH WITH THESE I made this mistake and my 261 mosa died.

I very recommend finding a good crossbow first a journey or higher

Platform saddles for these things are quite buggy on mobile/UME.

When getting stung by jellyfish,i got teleported to the middle of the map on the sky, only standing on a model of the saddle without my mosa. I dismounted, fell, died, tried finding my mosa, its just gone. This can also happen with plat quetzals upon being submerged, so in general, dont platform saddle flyers and aquatics

A max level, imprinted mosa with a high armor saddle is virtually unstoppable. I had a green one that I bred and named Jormungand after the world serpent in Norse mythology. It’s strength was mythical! (No pun intended)

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!

My mosa has 37k health and over 600 melee, I fear nothing in the water

NOW THAT YOU HAVE TAMED YOUR UNDERWATER GIGA, ENJOY DESTROYING UNDERWATER TEK TIER BASES. ;)

i tamed a lvl 145 x mosa with 600 arrows and 6.5 crossbows today

These creatures in real life actually needed to surface to breath much like whales, also they stayed near the surface of the water, never straying to deep.

Here is how to tame this guy, prepare lots of tranq arrows in a crossbow, then build a simple trap that works or if you wanna save resources, you can shoot it from an underwater resource cave or do it like a bronto as they are pretty slow. Once it's knocked out put narcotics or in it's inventory and exceptional kibble which worked best for me and you will have to wait. Once it's finished taming you can either slap a saddle or a platform saddle on and bam you have the giga of the ocean

Close you eyes and count to ten, or swim upwards

Not sure if its just my game on ps5 but just in case, I finally found a Mosasaurus, and then a few more. All of them were trapped in underwater rocks. I could only see the tail or their smiles. Just a tip if you're having trouble finding them. Since already trapped, I just tranq'd and used cryo to take them with me. Hope it helps.

My mosa has 14K HP and over 300 melee with an acendent platform saddle and he can kill anything in the ocean. Even alpha Mosasaurus and still have 13K health. (I play mobile.)

Underwater caves are very helpful for knocking these guys out. Always bring extra tranqs as this thing is basically the giga of the sea and torpor drops very fast.

Giga but in water, you see , you run

In mobile when hit by a jellyfish there’s a high chance that it can glitch out. Refresh the game and it will be fixed.

There is an option near the tranqs to switch to an x mosa. The new updates on here are freaking amazing, so don’t forget to utilize that for x mosa/any x creature taming :3