1. Get an ichthy with a saddle
2. Find a megalodon underwater
3. Kite the megalodon to shallow water with your ichthy
4. Tranquilize it from the shore or a rock safely
5. Make sure you don't keep shooting it after it is KO (I learned this the hard way)
6. Name it Bruce
I tamed mine by making it come to the shallows and getting it stuck by swimming in circles and using a club, you can get it early by doing this. I used a new club and when I was done it was at quarter health.
These terrors of the ocean may seem a very strong and a late-game tame, but my first megalodon was tamed when I was less than level 20, all I did was go into the water and lure it to a place shallow enough then knocked it with a club, took very long to knock out but it was worth that time.
Wild mantas can be fairly hard to hit with a megalodon.Just keep your shark still and the manta will often swim in front of its head.the rest is easy enough.with a high level megalodon even 120 mantas only take a few hits