Bring a dolphin so it follows you, bring it to the top of ocean, mini game time use sickle an remove leachs in a timely fashion then feed it wait an do it again etc (Looks like it's a kibble tame exceptional or extraordinary it's like a bronto takes a while.

Level 100 saddle an has to be made in Tek rep

According to the dossier, now available on Discord, the method of taming is as follows. This hulking leviathan is a passive tame, however, to initiate the taming process you need a ‘school’ of Ichthyosaurs ( you’ll need a certain number of Ichtys to create the ‘school’), these will act as a distraction that enables you to do the next stage. Next, using a sickle, you swim to barnacle nodes on the Shastasaurus and harvest them. Assumably (since it doesn’t sate otherwise in the dossier) you have to repeat this several times.

Tame a dolphin, swim up to it and bring it to the water surface, that initiates a mini game with leeches that are on it, use a sickle and hit the leeches off, then swum to mouth and feed it extraordinary kibble, job done, just make sure there is no danger around, if it gets hit, taming % goes down to 0. Happy taming!

1.tame a dolphin (ichthyosaurus)and ride it

2.go to the shasta and it will do some communication with the dolphin

3.then it will follow the dolphin so make it follow you to the surface of the sea

4.there will be some things attached to the shasta's body and you have to remove them using a sickle

5.after you remove them go to it's mouth and feed it the kibble

6.repeat until tamed