Leonardo da Vinci sketched a submarine-like vessel intended for underwater travel.
His notes describe a craft with a sealed structure that could operate beneath the water. Leonardo was concerned that the design might be used secretly in warfare, so he reportedly withheld some details. The surviving material does not provide a complete, tested submarine with a practical propulsion and life-support system.
Leonardo’s concept belongs to the long prehistory of submarines. Later submarines required watertight hulls, ballast systems, propulsion, and methods for supplying breathable air. Those technologies developed gradually over centuries, especially from the seventeenth century onward.
The sketch is sometimes presented as a fully workable submarine, but that overstates the evidence. Leonardo demonstrated remarkable awareness of underwater engineering problems, yet there is no reliable record that he built or tested this vessel.