The ecological novel has become a staple of contemporary fiction, and rightly so. When people aren’t really listening to the drumbeat of scientists, it’s essential that our best authors take up their sticks as well. Heck, bang a cymbal.

Richard Powers was writing about nuclear radiation and chemical carcinogens when the Young Turks of today were still in their disposable diapers. He’s been piled in prizes, most recently the Pulitzer for “The Overstory,” a complicated narrative of communicating trees. And yet he himself is sort of a grand old oak of American letters: a towering, sturdy figure often overlooked for flashier species.

Powers’s new book, “Playground,” is an enchanting entry point to his work that swings open easily with just a few creaks.

The title is, as the best are, multifarious.

Nominally, it refers to the Reddit-slash-Facebookish internet platform founded by Todd Keane, a white billionaire who has been diagnosed, at 57, with Lewy body dementia. He is reflecting on the erosion of his intense school friendship with Rafi Young, a principled Black bibliomaniac turned NGO worker.

It also points to the central staging area of childhood, where personalities calcify and futures are forged (once opponents in chess and Go, Todd and Rafi are now battling for higher stakes). And more mind-bendingly, the vast expanse of the earth’s oceans, “a rainbow garden painted by Bonnard” where remoras hitch rides on manta rays, octopii chase each other in hide and seek, cuttlefish perform like light shows on the Las Vegas Strip and when conditions are exactly right there are massive, generative orgies: “coral sex parties.”

The news about the warming, rising ocean has been so very grim, many people just don’t want to hear it.

Like a visit to the big blue whale exhibit at the American Museum of Natural History, “Playground” reminds, with a spirit of fun and wonder, why the sea — an alien planet within a planet — is so very worth sustained attention. You start to understand the zeal that drove the doomed Titan explorers down to the shipwreck that continues to pulse with animal and bacterial life.

When he’s little, and his parents are fighting, Todd fantasizes about descending himself, if only to to the floor of Lake Michigan, where “all dramas sounded muffled, under the water.” But the real avatar of marine glory in “Playground” is one Evelyne “Evie” Beaulieu, whose father, an engineer, throws her as a skinny, nervous tween into the deep end to test an iteration of the Cousteau-Gagnan aqualung. She goes on to write a children’s book, “Clearly It Is Ocean,” that transfixes young Todd.

Evie has grown up into an obsessive professional diver, barreling through sexism and motherhood with the support of her very patient researcher spouse, a Doug Emhoff type who “exuded a pleasant brackish scent.” Powers drops plenty of wry lines here.

“The thing that had taken her almost two years to write took her husband a little more than two hours to read,” Evie notes ruefully of her book, in a universal writerly lament. “There was something terribly wrong with that equation.”

The novel leaps back and forth in time and place. But its ostensible central conflict takes place on the paradisic island of Makatea, in French Polynesia, where Rafi lives modestly with his wife Ina, a sculptor, and the two children they’ve adopted. They collect plastic waste, à la the Legos washing up on European coasts, for one of Ina’s projects — deciding not to disturbed a glass bottle colonized, like a little Titanic, by sponges and crustaceans. One man’s trash might be another organism’s treasure.

Evie, now a nonagenarian, is also there researching a second book, astonished at the biodiversity she finds even after a destructive period of phosphate mining. The island’s small population is poised to vote on whether or not to allow a modular floating city, financed by guess-who from Rafi’s past, to move there. “Seasteading” has the potential to improve human lives, at the expense of all the other beautiful creatures.

Powers, who published early on artificial intelligence with “Galatea 2.2” (1995) reintroduces it here with an all-knowing tool, a collaborative “nanny app” called Profunda, which ostensibly will help the skeptical islanders. And the late twist this device enables, whorled as a seashell, may leave even the highest VO2 max reader gasping a little for air.