An atmospheric debut novel about friendship as a force of both salvation and ruin, told across two catastrophes. Marissa is six when her mother dies, and her father, a marine biologist determined to finish his wife's research, takes her to Thailand. There she meets Arielle, whose parents own the resort where they live during the week, and the two girls form a bond of the total, consuming kind that childhood sometimes produces. On weekends they join the researchers on a nearby island, learning the reefs and the forests, learning to free dive and hold their breath for minutes, learning to move together as unconsciously as the manta rays they name. Tara Menon writes the underwater passages with real precision, and the novel's sensory world, warm water and coral and the particular boredom of a child among adults, is its most immediate pleasure. Then the 2004 tsunami arrives and separates the girls' lives permanently. The second half follows Marissa into adulthood as she reckons with what the friendship gave her and what it cost, and with the way a defining early attachment can make every later relationship feel provisional. Menon is interested in the asymmetries inside intimacy, in who gets to leave and who is left, and in grief that has no ceremony available to it. The result is a novel about the deep places, literal and otherwise, and about what it takes to surface.