Into The Drowning Deep by Mira Grant

Seven years ago, the Atargatis set off on a voyage to the Mariana Trench to film a mockumentary bringing to life ancient sea creatures of legend.

It was lost at sea with all hands. Some have called it a tragedy; others have called it a hoax.

Now, a new crew has been assembled to investigate. And they'll discover that whatever is down there is definitely no joke . .