What device did Leonardo da Vinci design to help a diver breathe underwater?

Leonardo da Vinci designed a diving suit to help a diver breathe underwater.

His concept included a protective suit, a mask, and tubes leading to the surface. The arrangement was intended to let a person remain below the water while breathing through an air supply connected to the surface.

Leonardo developed the idea while studying underwater operations, possibly in connection with military activity. His notebooks also contain designs for underwater equipment and methods of moving or working beneath the surface.

The proposal was not a modern scuba system: it depended on surface-connected breathing tubes rather than a portable compressed-air cylinder. Some historians also question whether the design could have worked safely at useful depths. Nevertheless, it shows Leonardo applying anatomy, materials, and mechanical design to a problem later solved by diving technology.