Very easy to tame if you know what your doing. First tame an Ichthyosaur. Then grab a crossbow and some tranq arrows and find one and knock it out. It is not be able to attack if you are on the Ichthy. As you are taming it, be sure to remain on the Ichthy unless feeding narcs, so other creature don’t hurt you. Vote up if this helped
If trying to tame one make like a wyvern trap on the bottom on the ocean and hive someone else shut it. I use a sarco to lead it in the trap. On the center you can make the trap right next to the air bubble to escaped in the Airr away from any attack range and have a keypad to shut it. This will allow you to use any tranq attack
1. Don't shoot their head, shoot their butt or body. (This is true, dont trust gamepedia)
2. It wont left deep sea, so u can easily stay out of deep sea border and KO them.
3. Make sure to kill everything else around it before start to K.O it.
Build a 3x3 trap on a plesio patform standing on pillars as far back and high as you can go.
Dunkleo and sharks won't be able to attack plesio from inside. Trank risk free. Swim away when it fell asleep. Similar to quetz, just no need to have back wall removed/placed to catch it, the will swim thru the wall if you move. Once inside , just stop moving and it's trapped.