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 it sown there is definitely no joke... 

'Grant's skillfully crafted story combines science, horror, and mystery into a gripping novel of terror on the sea. Readers will never look at mermaids in the same way again.' ― Library Journal 

Paperback / 496 pages