[A] reasonably entertaining, imprudently daft aquatic thriller.

The realism of the early scenes -- leaving aside Nancy's unaccountable willingness to be stranded alone in a remote place -- is replaced by increasingly silly scenes that lead eventually to a nonsensical conclusion.

About half of what is now going on in all cinema is the product of technological advances in film-making and The Shallows makes much more intelligent use of them than the superheroes do.

The Shallows stays afloat by keeping its premise fun, visceral and engaging.