The name of the boat is Truth, which is only one of the piquant details in Joshua Zeman’s seafaring documentary, “The Loneliest Whale: The Search for 52.” Another is a coda that audiences will appreciate sticking around for.
The cetacean in question — known as 52 because his call broadcasts at 52 hertz, a frequency believed unique among whales — was first recorded in 1989 by the Navy and was suspected of being a Russian submarine. Identified as a whale by the marine scientist Dr. William A. Watkins, who tracked the solitary signal for a dozen years until his death in 2004, 52 has since remained as unfollowed as a suspended Twitter account.
Was he even still alive? Zeman, a man who loves a mystery, determines to find out. As he assembles his low-budget, high-hopes expedition and recruits a team of experts, the film’s nerdery is unexpectedly endearing. Excited scientists strive to affix trackers to bucking sea creatures, and acoustic devices slide beneath the waves, opening like magic into the shape of inverted satellite dishes.
Neither slick nor propulsive, “The Loneliest Whale” gently combines aquatic adventure and bobbing meditation on our own species’s environmental arrogance. While the boat noodles along the Southern California coastline, Zeman ponders the bloody history of whaling and the “acoustic smog” that plagues oceans teeming with clattering container ships. Not until we heard the 1970 album “Songs of the Humpback Whale,” he notes — the best-selling nature recording in history, and not just because it pairs perfectly with weed — did we care to save the whales. He hardly needs to add, if only the Earth could sing.
The Loneliest Whale: The Search for 52
Rated PG. Running time: 1 hour 36 minutes. In theaters.