Cuvier’s beaked whales are among the most mysterious and adept mammals on Earth.

They can dive deeper and hold their breath longer than any other marine mammal. But biologists still know very little about them, because they only surface for a few minutes between most dives, taxing the patience of whale experts, as well as the ability of electronic tags to upload information, before the whales plunge again into the depths.

“When you’re looking for an animal that can hold its breath for the duration of a feature-length movie, it’s a matter of odds and time on the water,” says Greg Schorr, a researcher with the nonprofit conservation and tag development company, Marine Ecology and Telemetry Research.

A new study, published Wednesday in Royal Society Open Science, is the first to look at a population of these whales that lives off Cape Hatteras, N.C. Researchers tagged 11 Cuvier’s beaked whales for an average of a month, tracking the length and depths of their dives.

The whales dove almost continuously. They took deep dives of about a mile, swimming a half-hour down and the same back up. These were followed by several shallower dives of about 918 feet — nearly two-tenths of a mile — lasting from 15 to 20 minutes, the study found. (The deepest scuba dive on record was 1090 feet in 2014.) The whales would spend an average of just over two minutes at the surface, before plunging again.