Marine biologists once treated coral bleaching—the loss of the algae that give coral its color and much of its food—as a near-certain death sentence. Newer fieldwork tells a more complicated story: some bleached colonies, if the surrounding water cools quickly enough, reacquire their algae and recover, and a few even return hardier than before. That window for recovery, however, is narrow, and it shrinks as marine heat waves grow longer and more frequent.