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

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

His underwater breathing apparatus appears in notes associated with studies for military engineering in Venice, where an underwater attack on enemy ships was contemplated. The design included a mask, breathing tubes, and a system connected to a floating device at the surface. Leonardo also considered ways to keep the tubes from collapsing and to provide air to the diver.

The exact form and intended operation remain subjects of interpretation because Leonardo's notes are incomplete and the device was not documented as tested. The design is often linked to the broader history of diving equipment, but it was not an autonomous underwater vehicle or a modern scuba set. It shows Leonardo considering practical problems such as buoyancy, air supply, visibility, and underwater movement. Later diving technology required improved materials, compressed air, valves, and reliable pressure control.