I'm not sure if this was a coincidence or not, but when trying to kill one (after the mantas), a swarm of eels came to fight me. It was my first time encountering eels and almost cost me a high level megalodon. Proceed with caution.
Extremely op I 1v2d a lvl 125 and 95 squid with a lvl 15 raw meat tame whale. After a long fight I killed both easily. I recommend putting in health stam and melee so that u can stay under longer, stand in fights longer, and hit harder