I tamed mine with a baryonyx to kill the manta bodyguards. The time between the first and second feeding interval takes a while, so sit back and grab some coffee while you wait. Regular meat will do as after the second feeding, the interval is only about 10 seconds. Make sure you keep all Megalodons and other mantas away from it while taming. I absolutely love mine for alpha killing and bio toxin farming. Also they get a crap ton of hit points per level up, almost 400.
This creature is so easy to tame. All you need is:
1. An Ichthyosaurus(these guy won't be attack by any water creature, except the jellyfish)
2. Anykind of meat(I suggest using prime meat and don't use fish meat)
3. Find one of these creature
4. Feed it prime meat(It's a long time between the 1st and the 2nd feed, after the 2nd feed it's fast)
And then you get one of these, just be careful of the megalodons, they will attack right after it is tamed. I hope this is useful for you<3