What underwater breathing device did Leonardo da Vinci design with a mask, tubes, and a chest bag?

Leonardo da Vinci designed an underwater breathing device commonly called Leonardo’s diving suit.

The design appeared in Leonardo’s studies of water and underwater exploration. It included a face mask connected to breathing tubes, with the tubes leading upward toward the water’s surface. A chest bag was intended to help the diver breathe underwater. The concept was designed for use by divers working secretly against enemy ships in wartime.

Leonardo’s design was not a modern scuba suit. It depended on air from above the water and lacked modern compressed-air cylinders, regulators, and reliable waterproof materials. The drawings therefore show an inventive concept rather than a documented working apparatus.

The design is sometimes confused with Leonardo’s other studies of swimming, diving, and underwater breathing. His notebooks contain many proposals for water-related machines, but the mask-and-tube apparatus is the one generally identified as his diving suit.