Long before the Trieste made its historic descent, scientists had discussed using small, maneuverable submersibles specifically designed for scientific observations to explore the ocean. It was Jacques-Yves Cousteau, coinventor of the original scuba-diving apparatus, who developed the first submersible used in undersea research. His little yellow Soucoupe Plongeante (Diving Saucer), launched in 1959, could carry two people to a depth of 300 meters (990 feet)—later increased to 410 meters (1,350 feet). The saucer's small size and maneuverability enabled it to travel along ridges and into canyons. Although a sphere is known to be the safest shape for a submersible's pressure hull, where its passengers ride, Cousteau opted for a flattened sphere for the Diving Saucer. This shape permitted the passengers to stretch out comfortably in a prone position rather than having to sit upright in a cramped spherical space.
Probably the world's most famous submersible is Alvin, operated by the Woods Hole Oceanographic Institution (WHOI) in Massachusetts. Alvin was launched in 1964, and was capable of diving 1,800 meters (6,000 feet). Its steel pressure hull was designed to carry a pilot and two scientists. Like all submersibles still operating, Alvin has been upgraded many times. Its newest hull, made of titanium, has a depth capability of 4,500 meters (14,750 feet).
Alvin has made many important dives. In the early 1970's, it took part in Project FAMOUS (French-American Mid-Ocean Undersea Study), a three-year study of the Mid-Atlantic Ridge in which oceanographers sampled, mapped, and photographed the gigantic undersea mountain range. In 1982, while investigating hydrothermal vents near the Pacific ridges, researchers on Alvin brought up the biological samples that turned out to be the mysterious Archaea.