Born on this day in Saint-André-de-Dubzac, France, oceanographer and undersea explorer Jacques Yves Cousteau (1910–1997) published his first book, The Silent World, as a celebration of life beneath the Mediterranean Sea.

“The greatest resource of the ocean is not material but the boundless spring of inspiration and well-being we gain from her,” he explained.

During World War II, Cousteau served with the French Resistance and was awarded the prestigious Croix de Guerre with palm. In 1946, he established the Undersea Research Group and invented marine tools like the Aqualung, the anti-shark cage, and advanced underwater cameras.

“What is a scientist after all?” he once asked. “It is a curious man looking through a keyhole, the keyhole of nature, trying to know what’s going on.”

His voyages aboard the research vessel Calypso became legendary. “From birth, man carries the weight of gravity on his shoulders. But man has only to sink beneath the surface and he is free.”

In 1973, he founded the Cousteau Society to protect marine life and educate the public on ocean conservation. “If human civilization is going to invade the waters of the earth,” he said, “then let it be first of all to carry a message of respect.”