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
Make yourself a longbow with plenty of tranqarrows, then build a big enough cage going from shore into the water with trapdoor and ladder close to the Dino gate, build a small platform to shoot from. Get it to chase you and wait for it to come thru the gate, then close the gates to trap it and fire on it till it K.O