Three weeks at sea. Two researchers. One chance to evolve.

"What would Charles Darwin do?"

In Charlie Bowen's twenty-six years of life, the motto has never failed her. Until now. She's confident the naturalist wouldn't know what to do if he were stuck at sea with Mateo Alvarez. Throw him overboard, most likely.

Participating as a scientific advisor on the SeaStar research vessel is Charlie's dream come true. However, her fantasies never included a documentary film or cohabitation in tiny quarters with her sworn enemy. Despite her exhilaration to uncover what lurks in the ocean's depths, she's wholly unprepared to discover something far more revolutionary at the surface—with Mateo, it's hard to hide the scars of her past. Worse, she may not want to.

For years, she's abided by a strict set of guidelines to keep her heart safe. Her life begins and ends with her best friend and PhD work. Yet with every lingering glance, broken rule, and stolen kiss, Charlie begins to rediscover parts of herself she once considered lost.

But life at sea is not the real world—a reality that continues to haunt her, even miles offshore—and as the two move into unknown territory with each other, there's one question that matters most: Can their relationship evolve into something spectacular, or are they doomed for extinction?