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
To knock out these easily, you should use an ichthyosaurus and crossbow with tranq arrows. You will need a lot of tranq arrows. Stay on the ichthyosaurus so the dunkleosteus won’t attack you. Don’t let anything dangerous get in the way. Hope this helps.
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.