Whilst free diving in the Tonga Archipelago last month, underwater 'photo-naturalist' Tony Wu had an experience he will never forget: swimming with a singing humpback whale. Humpbacks produce the longest and most varied songs in the animal animal kingdom – but these guttural growlers aren't always easy to find. 

"[Humpback] singers aren’t always so obliging," Wu explains. "Many swim as they sing, making it impractical to track them; others are so deep or in areas with such low visibility that you can’t find them; some stay down so long it gets mind-numbing boring; and others take off at first hint of pesky people."

But this whale (seemingly unfazed by Wu) sounded in the classic head-down position just 15-20 metres below the surface for the duration of the dive ... and thanks to Wu's fellow cameraman Michael Bonneau, we all get to enjoy the bass-heavy song of a male humpback in the wild!