BOOK REVIEW : Audacious Tale Traces a Life Lived 3 Ways : AQUAMARINE<i> by Carol Anshaw</i> Houghton Mifflin $19.95; 197 pages

In fiction, an epiphany is a flash of revelation or insight that transcends the events of the story and gives them a meaning more brilliant than themselves.

We have epiphanies in real life, but they tend to come, not at life’s climax, but back toward its beginning. After that gunpowder flash in late childhood or adolescence, that cosmological Big Bang, what follows can seem like a prosaic trek, the predictable orbit of a cooling planet. Whatever we achieve is a municipal affair compared to the lost kingdom.

Carol Anshaw begins her fresh and unfettered first novel with just such a detonating moment. She places it, improbably, in the life of a 17-year-old Olympic swimmer in the hours leading up to, and including, the finals in the 100-meter sprint. I say “improbably” only because Olympic competition is a broader-beamed and more popular setting than our art-fiction writers tend to choose.

The flash that starts the book, only four pages long, has an extraordinary sensory concentration. There is the out-of-body tension of Jesse preparing to mount her poolside chock, the launch, the brief churning maelstrom, the flip-turn and the slap on the tiles at the finish. It is physical ordeal as hallucinogen, in a world of prismatic glints and fractured aquamarine planes. It is water recounted by a fish.

And to add the other element of detonation, there is the odd exchange of glances between Jesse and Marty, her Australian rival, who beats her by three-tenths of a second. In the days before the event, Marty has seduced Jesse, an innocent from New Jerusalem, Mo., into her first sexual experience. Worse, she has maneuvered “you against me” into “you and me against the others.”

Has Jesse been bilked into losing her edge? Anshaw, who is as clever as she is original, never lets Jesse be sure--though we are--nor quite decide whether she did, in fact, relax into second place. That doubt, her virginal introduction simultaneously into sexual passion and evil and the Olympic intoxication combine into a formidable charge.

And Anshaw lets it go off in a remarkably audacious fashion. Her Big Bang produces not one but three Jesses. “Aquamarine” tells of the different lives that she might have lived. There is no “might have” in the telling, however; each of the three stories is a real one with an autonomous protagonist. What links them is a single golden and terrible memory; what separates them is a chance event.

After the Olympics a sports clothing representative offers Jesse a promotional tour. The first Jesse declines, the second accepts but rebuffs the agent’s sexual overtures, the third accepts them and marries him.

Jesse One stays in New Jerusalem, marries a kind and funny local boy, lives serenely helping him operate a tourist cave his family owns and has a baby. Jesse Two moves to New York, becomes an English professor and has a lover, Kit, who plays a sluttish woman on a television series. Jesse Three runs a swimming school in Florida with her husband. When he leaves her, she struggles to raise their two children and squeeze a living out of the swimming establishment.

Anshaw tells each of these three stories with appealing naturalness, touches of wry humor and a gift for characterization. Some of her people are hasty sketches or more ambitious, but not fully realized, portrayals. Others resonate.

Neil, the first Jesse’s seemingly placid and conventional husband, turns out to possess both wit and endurance. When the third Jesse’s sleazy ex-husband comes back to see his children, she suggests he take their troubled son back with him and get him a job.

“He nods, as if slowly contemplating the wisdom of the suggestion. Jesse can see him synchromeshing through the gears to get to the reason he won’t be able to.”

The most remarkable figures, not surprisingly, are the three Jesses. The two who have chosen relatively conventional lives have a sneaky wildness inside, an unextinguished fuse from the Olympic explosion. The first Jesse has a comically tentative lover who is learning to sky-write.

The third Jesse, who has had her fill of high-flying men, takes a lover who is remarkably like Neil. The lesbian professor, on the other hand, yearns for family and stability. And all three take chances for the ghostly lives they have not chosen. It is the cheerfulness, the zany energy of these chances that keeps the book moving.

Of the three stories, the first and the third are the best. The second Jesse’s story is thinner and, oddly, more sentimental. Anshaw has taken a risk in drawing these lives out of a common memory. It could have been schematic and artificial; instead, although there are awkwardnesses, it works exhilaratingly.

Next: Elaine Kendall reviews “An Intimation of Things Distant: The Collected Fiction of Nella Larsen” (Doubleday/Anchor Press).