The dossier says they're passive to humans and only attack little fish THIS IS NOT TRUE THEY WILL EAT YOU AND THEY TEAM UP WITH ELECTROPHORUS TO KNOCK OUT YOUR MOUNT AND SHARE IN THE FEAST AFTERWARDS!!

Plesiosaurs will team up and try to kill you

There is a group of them by herbivore island, but watch out for the Tuso(giant squid)

You're gonna need about three fiddy, then this beast will let you go.

This has to be the most terrifying creature on ark. I've tamed one and it still makes me piss my pants when i see it.