In his first book, The Silent World: A Story of Undersea Discovery and Adventure, Cousteau surmised the existence of the echolocation abilities of porpoises.

The two neighbors took the first ex-aequo prize of the Congress of Documentary Film in 1943, for the first French underwater film: Par dix-huit mètres de fond (18 meters deep), made without breathing apparatus the previous year in the Embiez islands in Var, with Philippe Tailliez and Frédéric Dumas, using a depth-pressure-proof camera case developed by mechanical engineer Léon Vèche, an engineer of Arts and Measures at the Naval College.

[6][7] Having kept bonds with the English speakers (he spent part of his childhood in the United States and usually spoke English) and with French soldiers in North Africa (under Admiral Lemonnier), Jacques-Yves Cousteau (whose villa "Baobab" at Sanary (Var) was opposite Admiral Darlan's villa "Reine"), helped the French Navy to join again with the Allies; he assembled a commando operation against the Italian espionage services in France, and received several military decorations for his deeds.

At that time, he kept his distance from his brother Pierre-Antoine Cousteau, a "pen anti-semite" who edited the collaborationist newspaper Je suis partout (I am everywhere) and who received the death sentence in 1946.

During the 1940s, Cousteau is credited with improving the Aqua-Lung design which gave birth to the open-circuit scuba technology used today.

According to his first book, The Silent World: A Story of Undersea Discovery and Adventure (1953), Cousteau started diving with Fernez goggles in 1936, and in 1939 used the self-contained underwater breathing apparatus invented in 1926 by Commander Yves le Prieur.

In 1946, Cousteau and Tailliez showed the film Épaves ("Shipwrecks") to Admiral Lemonnier, who gave them the responsibility of setting up the GRS (Groupement de Recherches Sous-marines, Underwater Research Group) of the French Navy in Toulon.

In 1947, Chief Petty Officer Maurice Fargues became the first diver to die using an Aqua-Lung, while attempting a new depth record to 120 m with the GERS near Toulon.

[8] In 1948, between missions of mine clearance, underwater exploration and technological and physiological tests, Cousteau undertook a first campaign in the Mediterranean on board the sloop Élie Monnier,[9][10] with Philippe Tailliez, Frédéric Dumas, Jean Alinat and the scenario writer Marcel Ichac.

Cousteau and the Élie Monnier then took part in the rescue of Professor Jacques Piccard's bathyscaphe, the FNRS-2, during the 1949 expedition to Dakar.

The adventures of this period are told in the two books The Silent World (1953, by Cousteau and Dumas) and Plongées sans câble (1954, by Philippe Tailliez).

In 1950, he founded the French Oceanographic Campaigns (FOC), and leased a ship called Calypso from Thomas Loel Guinness for a symbolic one franc a year.

With the publication of his first book in 1953, The Silent World, Cousteau correctly predicted the existence of the echolocation abilities of porpoises.

He reported that his research vessel, the Élie Monier, was heading to the Straits of Gibraltar and noticed a group of porpoises following them.

[2] Afterward, with the assistance of Jean Mollard, he made a "diving saucer" SP-350, an experimental underwater vehicle which could reach a depth of 350 meters.

[2] He directed Précontinent, about the experiments of diving in saturation (long-duration immersion, houses under the sea), and was admitted to the United States National Academy of Sciences.

[2] In October 1960, a large amount of radioactive waste was going to be discarded in the Mediterranean Sea by the Commissariat à l'énergie atomique (CEA).

A meeting with American television companies (ABC, Métromédia, NBC) created the series The Undersea World of Jacques Cousteau, with the character of the commander in the red bonnet inherited from standard diving dress intended to give the films a "personalized adventure" style.

In December 1972, two years after the volcano's last eruption, The Cousteau Society was filming Voyage au bout du monde on Deception Island, Antarctica, when Michel Laval, Calypso's second in command, was struck and killed by a rotor of the helicopter that was ferrying between Calypso and the island.

On 28 June 1979, while the Calypso was on an expedition to Portugal, his second son Philippe, his preferred and designated successor and with whom he had co-produced all his films since 1969, died in a PBY Catalina flying boat crash in the Tagus river near Lisbon.

In June 1990, the composer Jean Michel Jarre paid homage to the commander by entitling his new album Waiting for Cousteau.

[19] In 1992, he was invited to Rio de Janeiro, Brazil, for the United Nations' International Conference on Environment and Development, and then he became a regular consultant for the UN and the World Bank.

[20] This resulted in Jean-Michel Cousteau being ordered by the court to not encourage confusion between his for-profit business and his father's non-profit endeavours.

He discovered in him a man of prayer whom he accompanied in his last months of his life, giving him, through the sacraments of the Church, the strength of his passage towards eternity.

"[22] In a chapter entitled "The Holy Scriptures and the Environment" in the posthumous work The Human, the Orchid, and the Octopus, he is quoted as stating that "The glory of nature provides evidence that God exists".

[25] An homage was paid to him by the town by naming the street which runs out to the house of his birth "rue du Commandant Cousteau", where a commemorative plaque was placed.

The so-called "divulgationism", a simple way of sharing scientific concepts, was soon employed in other disciplines and became one of the most important characteristics of modern television broadcasting.

His Oceanographic Museum in Monaco, and perhaps even he himself,[26][27] has been identified as introducing the "Killer Algae" Caulerpa taxifolia, which are negatively affecting the Mediterranean's ecosystem.

In 2007, the International Watch Company introduced the IWC Aquatimer Chronograph "Cousteau Divers" Special Edition.

The proceeds from the timepieces' sales were partially donated to the non-profit organization involved in conservation of marine life and preservation of tropical coral reefs.