When the Jesuit polymath Athanasius Kircher came to depict Atlantis in his 1665 book Mundus Subterraneus (‘The Underground World’), he showed it as a great island in the centre of the Atlantic Ocean, hemmed in on one side by Africa and Spain and on the other by America. The map is orientated to the south, a Dutch cartographic convention at the time but one that is disconcerting to the modern eye – it’s as if getting to Atlantis requires a conceptual leap that puts it beyond reality. In the previous century, geographers attempting to understand the New World placed Atlantis in the Americas, while cosmographers influenced by the Neo-Platonist idea of harmonia mundi saw it as another, ‘better’ world, balancing their own. The dichotomy between Atlantis as somewhere to be discovered and as a concept has existed since Plato first wrote about it in the fourth century BC in his dialogues Timaeus and Critias. Was Atlantis an allegorical imagining, created by Plato as part of a foundation myth of ancient Athens, or was it truly a place, stories of which had been passed down by the priests of Sais in Egypt, derived, perhaps, from memories of an ancient flood or a Bronze Age catastrophe?

Atlantis is also the name of the submerged ancient city of Jules Verne’s Twenty Thousand Leagues Under the Sea, and that is how Damian Le Bas first conceives of it in this beautifully written book. As a child growing up on the south coast of England he dreamed of Atlantis, ‘a place of ruins: columns, arches, towers, walls caressed by soft blue light, invaded by fishes, wide-eyed at the broken palaces where waterweeds grow’. Years later, standing at his father’s deathbed, ‘in that first cold shock of grief’, he imagines the breathing tube coming out of his mouth as a snorkel, and thinks that the only way of reaching him again is by going underwater. The sea both fascinates and terrifies him, something he associates with his Romany background (in Romany culture, ‘the power of water is feared’). We follow his first tentative steps as he learns to dive, and then accompany him as he explores submerged ruins – of the Roman town of Baia in the Bay of Naples, of the pirate capital Port Royal in Jamaica, of the ancient city of Pavlopetri in the Peloponnese.

The narrative is full of delights and surprises. After describing Plato’s Atlantis, Le Bas takes us straight into the water – in Shadwell Basin in London, of all places. There, the ruins are not of ancient temples but of ‘shopping trolleys and motorcycles, now the furniture of fish … like petty criminals, repeatedly hooked and tackled and photographed, then thrown back into their shady underworld’. Here, as elsewhere, the scene is beautifully observed, often with a touch of humour. Swimming on the surface of the basin, he experiences the transformative sense of being in water – ‘the seconds disperse like ink, and the grime of quotidian worries dissolves away’. Few since the time of Jacques Cousteau have written so well about diving, about the heightened awareness that comes underwater and about the thrill of being there. ‘I, who had always been terrified of the sea, of drowning, of the endless blue, was currently suspended at a depth of a hundred feet on the other side of the world. I was not only calm, but utterly content,’ Le Bas writes. As he discovers, the sea is a place where at depth there are no shadows and the light seems to come at you from all directions at once.

Le Bas is drawn as much to living things as he is to ruins – to starfish, their undersides ‘engaged in a constant Mexican wave of brainless, but potent, intent’; to hermit crabs, ‘tiny, frugal and timorous fiddlers’, with which he feels an affinity, having once lived in the back of a second-hand van; to an octopus, with which a small tug-of-war occasions a fascinating aside about advanced invertebrate intelligence and whether we can know what another being feels; and to seals, ‘the liquid perfection of their style, ribboning around us’. His interests are not confined to the animate: split flint pebbles ‘with their inner resemblance to a picture of outer space or of deep water, speak of the depth of time from which they also arose’.

And what of Atlantis? At Santorini in the Aegean, where a volcanic eruption and tsunami in the mid-second millennium BC destroyed a vibrant Bronze Age society and inundated coastal communities, he experiences ‘rapture of the deep’ (or nitrogen narcosis) as he dives into a caldera. The devastation caused by the eruption has led some scholars to argue for the historicity of Atlantis. At Helike in the Peloponnese, he sees where an earthquake in Plato’s lifetime caused the city to sink into a lagoon. But, as he shows, these lines of thinking about Atlantis – as an actual city or something based on reality – can never truly anchor it. It remains a place, like the Garden of Eden, that lies just over the horizon or just outside the diver’s field of vision.

The risks of diving mean that any discovery underwater can be exhilarating, and Le Bas sees some wonderful things. The Drowned Places is one of the best books on diving that I have ever read.