Similar to THE DESCENT (2005)

Forget The Shallows, I thought this was more like The Descent (2005).

Female thrill-seekers head-off on an exciting adventure trip to get away from their recent relationship issues. They get trapped alone in the dark and find themselves hunted by man-eating creatures in their natural habitat. They split up and are seemingly always trying to find each other in the dark and use flares. In the end the lone survivor hallucinates and we're given two possible endings depending on our interpretation.

Actually its similar to The Shallows in that we're given a character with another useless emotional backstory. In The Descent that backstory at least has significance later in the film and created tension with one of the other characters.

In The Deep is very tense and scary...almost too scary. Its set mostly in the dark with just the two girls and was quite clausterphobic. It would have been great if we were given relief now and again by showing us what was happening on boat above the surface but I guess the director wanted us to feel what the girls feel. I really wanted to see the sharks more though. Its not as stupid as The Shallows and thankfully not as stylised but I still think it over-does it in the scares department. I found it quite uncomfortable to watch which is not the same as scary.