When most people think of Jacques-Yves Cousteau, they picture the red beanie, the Calypso ship, and schools of fish drifting across turquoise seas. But Cousteau was more than a filmmaker and explorer – he was an inventor with a knack for the unconventional. And few of his creations captured the public’s imagination quite like his “flying saucer” submarines.

A Submarine That Looked Like Science Fiction

In the mid-1950s, underwater exploration technology was still rudimentary. Submarines existed, but they were often bulky, military-focused, and difficult to maneuver in shallow waters where much of marine life thrives. Cousteau wanted something agile, something that could give divers an almost spaceship-like ability to hover and glide through the undersea world.

In 1959, Cousteau and engineer Jean Mollard introduced the SP-350 “Denise”—nicknamed la soucoupe plongeante (“the diving saucer”). The resemblance to UFOs wasn’t accidental: the two-man craft was a sleek disc about 3 meters across, with a central dome of clear acrylic for a panoramic view.

How the Flying Saucer Worked

The SP-350 was designed for shallow to mid-depth diving—down to about 350 meters (1,150 feet). It was battery-powered, with electric propellers and a unique vertical thruster that let it “hover” in place or move straight up and down like an elevator.

The sub’s design allowed for, maneuverability in tight reef environments, silent operation, which meant marine life wasn’t frightened away, and long observation sessions without exhausting the crew, since they were protected from the cold and currents.

From the sub, Cousteau and his team could steer with a joystick, operate external lights and cameras, and even deploy small tools for collecting samples.

Missions Beneath the Waves

Cousteau used the flying saucer in numerous expeditions during the 1960s and 1970s. The Calypso often carried the SP-350 on its deck, ready to be lowered into tropical lagoons, coral reefs, and archaeological dive sites.

Some notable uses included:

• Documenting reef life in the Red Sea and Indian Ocean with unprecedented stability for filming.

• Exploring underwater caves and shipwrecks, where traditional submarines couldn’t navigate.

• Studying marine behavior at close range—allowing scientists to record natural interactions without diver interference.

The craft became a star of Cousteau’s television specials, giving audiences at home the feeling they were aboard a sci-fi vehicle cruising an alien world.

A Legacy in Design and Inspiration

The SP-350 “Denise” was eventually retired, but its influence can still be seen in modern submersibles and remotely operated vehicles (ROVs). Cousteau’s playful yet practical approach—combining whimsical design with scientific purpose—helped inspire a generation of oceanographers, engineers, and curious kids.

While the flying saucer may not have traveled to outer space, it certainly made the ocean feel just as mysterious and otherworldly. For Cousteau, that was the point: to remind us that there’s a vast, alien frontier right here on Earth, waiting beneath the waves.