Use a high level Basilosaurus with high health to lead it to shallow water where the basilo gains health faster. Dismount and let the megalodon bite at your basilo while you traq it. Tamed 4 150 megalodon with this method works like a charm.
I spawned at a beach and the water was filled with a whole ton of Megalodons there was also spino nearby and killed everything I had so I let it into their territory the spino cleaned them out but then it died.
So like one time I went swimming,I went to the deep end, then I saw something, swimming VERY FAST, I (Being a noob NO JUDGE) had no idea what it was so..guys what I STAYED THERE!! Then the Megalodon ate me.Yeah but here is a tip...If you see a megalodon...RUN (if you don’t have the stuff RUN...If you do try to tame it)