There are some moments here of absolute non-spoken brilliance. Zooming in and out in the middle of a rapidly spinning dolly shot is an example that demonstrates how Shyamalan makes the most out of some simple techniques, his judicious framing and cutting, long shots and panning handles to depict the viciousness of time, aging and the despair of isolation in a devastating manner.
This also makes the latest work of Shyamalan a really provocative craft as I found its atmosphere to be one of the film's main strengths. A good thriller is also a good mystery and Shyamalan know this, he effortlessly toys with several tropes and motifs from classic thrillers (such as Creature of the Black Lagoon) to more contemporary sensibilities (like The Shining or The Sixth Sense-also directed by Shyamalan). Sometimes he makes us wonder whether the strange occurrences on this beach are produced by an unknown creature living on the water or on the caverns, or if they are imagined scenarios that come out from the paranoia of the characters. This atmosphere that swings between material reality and delusion, and between survival and horror is what makes this odd and simplistic story gripping and successful on its visual execution and written concepts.
While the film is fluid and well paced visually-wise, it staggers on its narrative especially in the final act where is clearly evidenced that the pacing of this film is uneven and its ending is too reliant on verbal exposition. But besides, the brilliant directing of Shyamalan next to the ideals and concepts found on this story work indescribably well as a commentary on human's inherent fear of dying which make for an equally compelling and clever film that I don't see many directors nowadays daring to try.