The oceanographer Evie Beaulieu stumbles on her heart’s desire while surveying the wreckage of a second world war naval battle. Thirty metres down in the waters of Micronesia’s Truk lagoon, past the Japanese submarines that have become kelp gardens and the sunken warships teeming with fish, she alights on the skeletons of two sailors that have long since become coral sculptures. Momentarily starved of oxygen, Evie foresees her own death and her ideal resting state. She decides she wants to die at sea, become a reef and thereby secure a rich and strange afterlife.

Themes of transformation, loss and regeneration abound in Richard Powers’s Booker-longlisted Playground, a transcendentalist deep dive of a novel that at times almost caves under the weight of its ambitions. Ostensibly, it spins the tale of Makatea, a Polynesian atoll that finds itself preyed on by a consortium of shadowy Californian investors who want to build modular parts for vast floating cities. But that’s only the surface narrative, a protruding rock to navigate by. Playground freely references The Tempest with its framing of Makatea, an island haunted by its past and ripe for exploitation, and cites Arthur C Clarke, who said that the planet we live on should by rights be named Ocean. What we think of as Earth is “the marginal kingdom”, an ancillary to a main stage that occupies 70% of the globe. The real story – the real treasure – can be found in the water.

The sea calls most urgently to Evie, a character loosely based on the marine biologist Sylvia Earle, who abandons dry land every chance that she gets and belatedly writes a bestseller, titled Clearly It Is Ocean, as a means of explaining herself to her kids. But the thrill of the unknown – of the world beyond the one we know – is also what drives Rafi Young and Todd Keane, two childhood friends from Chicago. Rafi (a black honours student) and Todd (white, middle class) initially bond over games of chess, graduate to the Chinese strategy board game Go and then catch the first wave of generative AI; what Todd refers to as “the third industrial revolution”.

Todd, we gather, will go on to make billions from the launch of Playground, an early-noughties precursor to Facebook and Second Life, whereas the brilliant Rafi winds up working as a schoolteacher in Makatea, cut out of the profits from the site he helped brainstorm. But the story’s a trickster. It sloshes between time frames and switches from first and third person to the point where the drama becomes clouded and borderline hazardous. While wealthy, authoritative Todd serves as Playground’s chief narrator, the man now suffers from Lewy body dementia, a condition that impacts his language, thoughts and motor functions. In the grip of his symptoms, he hallucinates vivid marine life – spadefish, hammerheads and lemonpeel angelfish – scrolling across his bedroom wall at home.

What a lush, opaque world Powers conjures for us here. Just as Evie Beaulieu longs to interpret the “liquid text” of the sea, so the reader has to regularly reorient themselves in order to keep track of the plot’s braided streams. Playground is the American author’s 14th novel, although it carries tantalising echoes of its immediate predecessors. Like 2018’s arboreal epic The Overstory, it’s a book bewitched by the concept of intelligent alien life in our midst (trees there, fish here). As with 2021’s dystopian Bewilderment, it’s drawn to the virtual frontier of generative AI and its potential to both raise the dead and draft an alternative present. If the tale’s disparate elements (rites-of-passage drama, marine adventure, environmental cri-de-coeur) never entirely cohere, that’s probably as it should be. Playground works best as a fabulous exploration. It points out the sights, provides background and asks open-ended questions. After that, we’re largely on our own.

One has the distinct sense that the author is embarked on the same journey of discovery. He’s our wonderstruck guide to a planet that he’s still figuring out, periodically dazzled by fresh information, with a charming habit of chasing every new train of thought. Powers marvels at the seabed with the same wide-eyed fervour that Emerson and Thoreau evoked, gaping at the majesty of 19th-century New England. He thrills to its “Bonnard gardens” and “Miro sculptures”, and the way an octopus can repurpose a jar to make a protective glass shell.

Back on Makatea, the residents vote on the island’s fate, using black and white stones from the old Go board game. The oceans are warming, the reefs have all bleached and the people are torn between the known and the unknown, unsure which way to jump and what the future might hold. And it is here, at its most superficially schematic and decisive, that Powers’s great, tidal story folds in on itself – as Rafi and Todd are set on a collision course and 92-year-old Evie (“older than half the world’s current countries”) totters towards the ballot box. It’s a fitting finale for Powers’s rambling, rapturous tale in that it doesn’t feel as though it’s a finale at all; more like the hidden undertow of a breaking wave that only drags us further out to sea.