In 1979, Sylvia Earle walked untethered on the sea floor at a lower depth than any living human being before or since. In the so-called Jim suit, a pressurized one-atmosphere garment, she was carried by a submersible down to the depth of 1,250 feet below the ocean's surface off of the island of Oahu. At the bottom, she detached from the vessel and explored the depths for two and a half hours with only a communication line connecting her to the submersible, and nothing at all connecting her to the world above. She described this adventure in her 1980 book: Exploring the Deep Frontier.