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.
Bring more tranq arrows then you think! Mine took 100 at close range, on the body, at LEVEL 3.
I took cooked prime meat (stays better longer) and got mine in only four feedings. On an icthy they don’t chase (mobile player here) happy taming- Survivor Belle
If your on ark mobile grab a crossbow (a good one) a good underwater tame and the scuba set so you don't drown.i finnaly tamed a plesi with this method and now it's time for taming the dunki (I am coming armoured shark)