The world’s loneliest whale was discovered in 1989 when his mating call was picked up by US Navy underwater surveillance designed to detect Russian submarines. The frequency of the whale’s singing, at 52Hz, was much higher than other large whales. Was this guy the first of his kind, or the last? Could other whales understand him, or was the 52 a lonesome wanderer, crossing the ocean looking for love, singing into the darkness? The story went viral in 2004 after an article in the New York Times, inspiring hashtags – #TheSaddestThingEver! – and back tattoos.

Now comes this documentary, directed by Joshua Zeman and executive produced by Leonardo DiCaprio (he’s much easier to find than the whale, frequently sighted onboard a yacht with a supermodel). Zeman charters a boat called Truth and assembles a crack team of oceanographers to solve the mystery of the 52. Spotting the whale will be harder than looking for a needle in a haystack, warns one of the experts – and this is a film raised a fair few notches by the wonder of geekery, the absolute joy of seeing scientists living and breathing their work.

It’s no spoiler to say that a feeling of anticlimax is here from the start – though to be fair to Zeman, he does get a bombshell at the end. Before that, he fills out his film with some interesting backstory: beginning with a brief history of whaling, and including an upsetting sequence showing how noise from container ships in the Pacific interferes with whales’ ability to communicate, creating an entire ocean of lonely whales. Best of all is an interview with the environmentalist Roger Payne, whose hit 1970 album Songs of the Humpback Whale taught us how to love the whale. As he says: nobody cared about saving the whale until they realised whales can sing. Still, if the 52 is watching the message is loud and clear: stay the hell away from humans.

• The Loneliest Whale: The Search for 52 is available on 4 April on digital platforms.