A new study provides the first record of the diving behavior of Cuvier’s beaked whales in US Atlantic waters. The species is Earth’s deepest-diving mammal but spends very little recovery time at the surface. The new data, from 5,926 dives recorded off Cape Hatteras, N.C., shows them routinely diving more than a mile while holding their breath for over an hour. These whales push the limits of mammalian physiology.