Scientific modeling suggests that up to 18 unknown large aquatic creatures exist

Monsters of the deep still undiscovered:

"GIVEN their size, you might assume they had all been found by now. But scientists believe the world's oceans are still hiding giant underwater creatures which have yet to be discovered.

Marine ecologists have predicted there could be as many as 18 unknown species, with body lengths greater than 1.8 metres, still swimming in the great expanses of unexplored sea."