THE DELICATE RED filigree of the sea fan coral looked like alveoli in lungs, Clare thought as she kicked through the shallow waters of the reef, out towards a rock wall that she saw in the distance. She passed an orange coral grouper speckled with blue, stunning violet damselfish, the black-and-white striped bodies of the angelfish tipped with yellow. Behind her, Merrill was following a pair of juvenile turtles, their fins moving in a figure eight, bubbles trailing from his tank.

Six months ago, she’d taught him to snorkel near the shore. He mastered that quickly, and she drew him further into the ocean, until she became bored with the places they were swimming.