Aqua-Lung was the first open-circuit, self-contained underwater breathing apparatus (or “scuba”) to reach worldwide popularity and commercial success. Aqua-Lung was the brand of air regulator, which could be attached to gas tanks. This class of regulator is now commonly referred to as a diving regulator, or demand valve. The Aqua-Lung was invented in France during the winter of 1942–1943 by two Frenchmen: the engineer Émile Gagnan and the Naval Lieutenant (French: “lieutenant de vaisseau”) Jacques Cousteau. It allowed Cousteau and Gagnan to film and explore more easily underwater.

https://en.m.wikipedia.org/wiki/Aqua-Lung