Liam Neeson

'The Shallows': Come on in, the water's Lively

'The Shallows': Come on in, the water's Lively

There’s an excellent movie now in theaters: a deeply moving adventure about a traumatized young female who plunges into unfamiliar waters and experiences terror and salvation by way of some computer-generated marine life. But enough about “Finding Dory.” If you’re looking for a quick and satisfying summer thrill — a reminder that all you really need to make a movie is a girl and a flare gun — then the aptly titled Blake Lively-vs.-shark thriller “The Shallows” should serve you nicely.

It serves Lively best of all. If Hollywood has seemed slow to appreciate this talented actress (the popularity of the CW’s...