Acoral reef in Indonesia thought to be dead has been discovered to be erupting with glorious uproar – the sound of fishes whooping and grunting as they communicate and search for food. It’s like Finding Nemo come to life. We shouldn’t be surprised. The ocean, like Prospero’s island in The Tempest, is full of strange noises. It crackles and it roars. Jacques Cousteau may have been a great ocean explorer, but when he made his film The Silent World in 1956, I wonder whether he was actually listening down there, through the bubbles of his aqualung. Sound travels five times faster in the water. The ocean is a giant conductor of sound, an aquatic internet for every organism in it. They feel it in their bodies, and as they create sound, they are physically reaching out: from pistol shrimps that snap their claws so loudly that the sound makes them seem a hundred times bigger, to the great whales who, as Roger Payne, the first person to record and release whale song, has observed, make a sound as big as the ocean itself, and which can be heard for thousands of miles. A humpback in the Caribbean can be heard by a fellow whale off the coast of Europe. At 230 decibels (an aeroplane 100 feet away reaches 140dB), sperm whales are the loudest animals on Earth. Diving with these cetaceans in three-mile-deep waters off the Azores, I had to sign a consent form from the islands’ government, waiving liability should my hearing be damaged. Indeed, when I was first echo-located by a large female sperm whale, I felt her sonar clicks judder through my body like an MRI scanner. American scientists first recorded humpback song in the Atlantic in the 1960s, when trying to detect the sounds of Soviet submarines during the cold war. Instead they picked up the eerie, fluting calls of whales. In the early days of whaling, sailors who heard these sounds through the wooden walls of their ships believed they were the ghosts of their drowned comrades. The recording of that sound, when released, actually saved the whales, because they suddenly had voices, a sense of culture and personhood. Deep below what Herman Melville called “the ocean’s skin”, sound is the only viable sense, adding mystery to a world we know so little about. In the 1990s it was believed that an unidentified and very loud bloop detected in the benthic abyss was the sound of an enormous animal, possibly a kraken-like squid. In fact it has been proved to be the noise of an Antarctic icequake. Such uncanny sounds have convinced us of mythical creatures. The keening calls of female grey seals gave rise to the idea of selkies, humans in seal skins – or the other way around. Sound artist Chris Watson used recordings of grey seals to embody A Song to the Siren, written by singer-songwriter Tim Buckley and poet Larry Beckett in 1967, its plaintive, elegiac tone evoking the call of the sea itself; and, perhaps, Buckley’s early death and of the sad drowning of his own son, his fellow singer Jeff Buckley, when swimming at night. The lure of the sirens is a myth dating back to Homer’s Iliad and beyond: the notion that we might be drawn in by its hypnotic sound. But it also speaks to our ignorance of the sea and what it means to other cultures. The Wild Coast of South Africa is currently threatened by sonic oil explorations by Royal Dutch Shell. Conservationists fear the use of “sound guns” will disrupt oceanic wildlife, from plankton to the southern right whales that breed in those waters. “Our ancestors’ blood was spilt protecting our land and sea,” Reinford Zikulu, one of the protest group Sustaining the Wild Coast, said. “We now feel a sense of duty to protect our land and sea for future generations.” The invention of steam engines, military sonar (ironically inspired by whales), and sonic surveys has created a cacophony threatening foraging fishes, the immune systems of mammals, and the social structures of many creatures. Yet the sound of the ocean remains the sound of life. Stick your head in any shallow sea and you’ll hear the crackling of shrimps and fishes as they grub for food in the sand or on a reef. It was a revelation to me when I first heard that sound. It made me realise the deep was not the fearful place I had imagined as a child, but a living entity, producing a beautiful music of its own. It was somehow reassuring. After all, we first experience sound through the salt water of the womb, the little sea inside our mother. Is that why historically the sea has been regarded as a “she”? When I was scanned by that matriarchal whale in the deep blue Atlantic, I had just lost my own mother. I’d appeared in the whale’s domain, trying to understand who she was. And she in turn was trying to work who I was, too. Philip Hoare is an author whose books include Leviathan, Or the Whale