Megalodon

8.0.0 UPDATE
Megalodon (meg-ah-lo-don, meaning “Big/Great Tooth”) is a huge hostile prehistoric shark that dwelled in various mid to late Cenozoic subtropical oceans. It was added in the 8.0.0 Build along with the 4 other "Mega Mobs". They are purely aquatic and highly aggressive, being one of the largest marine predators in the game next to mosasaurus, the only shark in the mod so far, and cathemeral, meaning they are active both during the day and at night. They are extremely dangerous, and can kill an unarmored player in one hit.

Females are approximately 13 blocks long and 4 blocks tall, and males are much shorter at 7 blocks long and 3 blocks tall. They are one of the only mobs where females are larger than males. Newborns are 2.5 blocks long, and are fully grown in 13 minecraft days. They, like the other apex predators, cannot be given essence of chicken to grow faster.

BEHAVIOR
Megalodon, like almost all other mobs, has a mood (seen with a DinoPedia) that can drop by being in an inadequate habitat, being overcrowded, being starved, or being attacked, and can be raised with food. Their mood cannot be raised by toys, as the megalodon will not play with any of the enrichment items including the aquatic bubble blower. Even at its highest mood, it will not stop being aggressive. Currently however, the hunting ai is bugged and so it will (probably) not attack you unless provoked.