We all need some downtime. In “The Shallows,” medical student Nancy Adams (Blake Lively) decides to get away from it all and ride the waves at a secluded beach in Mexico. Once in the water, she guides her surfboard out to a very dead and very bloody whale, only to discover the killer, a large vicious shark, lurking nearby. The seafaring killer apparently thinks that Adams’ fate should be the same as the whale’s. And that her “downtime” should be permanent.

“The Shallows” is an intense battle between human and beast. However, this is a story that we’ve seen over and over. In Alfred Hitchcock’s 1963 thriller, “The Birds,” Tippi Hedren comes under attack by a flock of birds gone mad. We saw it in Stephen King’s “Cujo,” where lead character Donna Trenton does battle with a rabid St. Bernard.

Also, as is often the case in horror films or these types of dramas, characters find themselves in these nightmarish situations because of a series of ostensibly bad decisions. Here, a young woman decides to go to an isolated beach in a foreign country all by herself.

Another problem with this story is the writers try too hard to make Adams a sympathetic character. She’s a medical student, which implies she’s both smart and caring. She calls to check in on her little sister from the beach. And there is also a subtext that her mother is dead and might have been killed at that very same location.

While Lively serves the purpose of the beautiful young heroine who is fit and athletic, her character is supposed to be from Galveston, Texas, which is in the southern part of that southern state. Yet Lively, who grew up in California, doesn’t have the slightest regional accent.

The positives are the film’s dramatic and intense scenes. There are some edge-of-your-seat clashes between Adams and the shark. We are accustomed to superhuman male protagonists, and it’s good to see female leads showing that same credibility-stretching strength and vitality.

Shot in Australia, the film has beautiful scenery, but frankly it’s not any better than what you’ll see on HDTV. That’s the problem: With so much entertainment available on big-screen TVs and at our fingertips on our laptops and phones, movies have to offer us something exceptional, and “The Shallows” simply doesn’t. It’s a Rent It—engaging but not worth the trip to a theater.

The film is PG-13 for bloody images, intense sequences of peril and brief strong language, and it is appropriately timed at a relatively brief 87 minutes.