For all the successes of dinosaurs on land, they never made it into the sea - that is the realm of an entirely different group of reptiles, no less successful and no less awesome. The Jurassic sea boasts the largest carnivore on the planet: Liopleurodon, at 25 meters this monster was the same size as a blue whale but armed with teeth that were a quarter of a meter long. And Ophthalmosaurus - the fastest animal in the sea with huge eyes for night time hunting.