Denise was her original name, and she was the first underwater vehicle designed expressly for scientific exploration.
Developed by Jacques-Yves Cousteau and engineer Jean Mollard at the French Center for Undersea Research, the vehicle was dubbed the SP-350 or, less formally, " diving saucer ", because of its resemblance to the flying saucers of science fiction.
From 1959 on, the mini-submersible sailed the depths to explore unknown parts of the ocean. On board Calypso, a crane lowered the saucer into the water or lifted her up to the rear deck of the ship. With a diameter of 2.85 meters and a weight of 3.5 tons, she carries a crew of two in her steel cabin.
She can work stay as far as 350 meters down, for four or five hours.
The saucer moves just as a squid does, with an ingenious but simple jet propulsion system: water is drawn in from the outside and squirted back out through two tubes. With these jets, the saucer can move along underwater at a speed of 2 knots, or about 3.7 km/h. The two people inside are stretched out on mattresses, watching their surroundings through tilted portholes that let them come within a few centimeters of their subject.
The deeper the submersible goes, the darker the water, so three movable lights illuminate the " world without sun " at different angles. They can even light small objects up to 10 meters away and so reveal creatures that people have never before observed.
Onboard equipment includes two cameras, a radio and a tape recorder. The saucer is also furnished with a sampling arm, controlled from inside the cabin. Looking like a space ship, the diving saucer is perfectly suited to the environment in which it must work.
After tests, Denise became a permanent part of Calypso's armory and, today, it has more than 1,500 dives to its credit. Denise is the oldest sibling of scientific submersibles and opened a new era of underwater research.
In 1965, technology had evolved enough to allow for the construction of two new, more advanced one-man diving saucers. These little twins were baptized Sea Fleas and can descend to 500 meters.