Even when it feels awfully familiar, “The Shallows”- starring Blake Lively as a woman who finds herself attacked by a white shark while vacationing on a Mexican beach- immediately held me in its grip. What follows the attack is a gripping story of one woman’s resourcefulness and determination to stay alive. Since that woman is the charismatic Lively, it’s easy to root for her and pay attention through her many trials…up to a point. Directed by Jaume Collet-Serra, “The Shallows” is a well shot, even experimental film, but it also doesn’t know when to quit, and that’s why I didn’t fully enjoy it. At a certain point, I stopped caring and that’s when I realized that the movie was wearing me out. It’s still remarkably executed and Blake Lively does a fine job. I just wish the overall result had left me feeling satisfied instead of indifferent.