How to tame a Deinosuchus:

Find one (Beaches, Rivers, Swamps, I found mine on the beach in the southeast corner)

If it is in water, lure it out by aggroing it onto you) repeat this every time it goes into water

Wait until it opens it’s jaw, run up to it with kibble or meat and press „E“ to put it in its jaw. Instantly after pressing E, turn and run away, since it’s jaw will slam shut and it wakes up. Repeat this process until it’s tamed.

Leftclick: Regular Bite

Rightclick (Hold until 100% charged): Giga Bite, deals A TON of damage and has a short cooldown

C: Tail swing deals A TON of knockback

Hold Space: Makes it turn into the direction you are looking at

Good Luck