What human-powered underwater suit did Leonardo da Vinci design for divers?

Leonardo da Vinci designed a diving suit for underwater exploration and military operations.

His 15th-century concept included a leather suit, a mask, breathing tubes, and a system intended to keep the diver supplied with air. The design was associated with plans for covert underwater activity, including damaging enemy ships in a harbor.

Leonardo’s suit was a concept rather than a tested modern diving system. It should not be confused with a diving bell, which provides a shared air space, or with later hard-hat diving equipment. Modern scuba gear uses compressed gas cylinders and regulators, technologies unavailable to Leonardo.