Thanks to Hollywood, dinosaurs, in the popular imagination, are always stomping around on land wreaking havoc. But, the seas had giant creatures too.
Take Elasmosaurus, for example. This plesiosaur lived in the Late Cretaceous, some 80 million years ago. More than 40 feet long, and weighing a couple of tons, its exceedingly long neck -- more than half its overall length -- made the animal incapable of lifting anything out of the water except its head.
Watch this seafaring giant and a couple of other marine animals, in this CGI imagining of the ancient seas.
Note: An earlier version of this post incorrectly referred to Elasmosaurus as a dinosaur. Elasmosaurus was not a dinosaur but a genus of plesiosaurs, which were a group of marine reptiles.