Always use a bola when trying to knock out this dino, once your in its mouth you might as well give up so make sure you have 2-5 bolas and plenty of tranqs. If necessary us an argentavis to pick it up and put it into a taming pen (preferably 3X3) and knock it out like that.
So I kinda wanted to tame one so I went to grab one with my argy…
He grabbed me off the argys back fell into the water with him I pulled out my sword and killed him then all the STUIPED TORPOR DEALING SNAKES CAME AT ME I made it out alive but I almost drowned while I was knocked out I made it to my nearest outpost from there I grabbed my pteranodon and flew to whistle my argy and flew home
PS: it is useful to have outposts where you can retreat also the outposts should have a flyer and supplies. I have 1 in redwoods 2 next to diff parts of swamp and some others through the map