1: Do not fight them in water under any circumstances
2: Lure them on to land
3: Use a bola
4: Attempt to Tranquilse with bow and arrow or better
Remember: They can only be tamed with fish meat and they usually kill all the fish in the area so you should probably have some prepared beforehand.
Copped a lvl 50 pretty easily. Just bring lots of tranqs and bolas. Yep that’s right! They can become victims of the trusty bola! That means you can get one at a fairly early level; although, this goofball won’t be super useful until you’re high enough to get the saddle.