Leonardo da Vinci’s concept for helping a person breathe underwater from a floating bell was a diving bell.
A diving bell is a chamber that traps air underwater, allowing a diver to enter and breathe for a limited time. Leonardo’s underwater studies included arrangements in which a bell or air reservoir supplied breathable air while remaining connected with the surface. These ideas formed part of his interest in underwater exploration and naval engineering.
The principle depends on air being trapped inside an inverted chamber. As the bell descends, water rises inside it and compresses the remaining air, reducing the available breathing space. The depth and duration therefore depend on the bell’s volume, pressure, and the diver’s activity.
Leonardo’s sketches are often mixed up with his full diving-suit concept. A diving suit encloses the diver and uses tubes or an air supply, while a diving bell provides an air-filled chamber. Leonardo proposed related underwater devices, but no successful Leonardo-built apparatus is documented.