For Beginners: Get atleast 7 Tranq arrows,or more.

First,You have to Lure a Baryonyx to a rock it can't climb.

Second: fricking shoot Tranq arrows at it

Third: Feed it Prime fish meat/Fish meat (Kibble is the best one) for mobile,it likes Pachyrhinosaurus Kibble.

Fourth: Now you got the best Semi Aquatic dinosaur,It can also do Caves (But not lava ones).