Around 1500 Leonardo da Vinci moved to Venice which was at war with the Ottoman empire. There he devised an underwater breathing system to be used as a means of raiding the Ottoman fleet so that divers could drill holes in the bottoms of the enemy ships.
Housed now in the Codex Atlanico, da Vinci created a sketch of a system that employed a floating bell made of cork, tubes crafted from hollow cane reeds, and a bag-like hood to cover a divers face. The floating bell of cork kept the ends of the reed tubes above water so that the diver below could breathe air from the surface. The plans included weights to help keep a diver below water and a valve adjustable bag that could fill with air to assist in resurfacing. da Vinci even planned for divers to stay submerged for some time, as the leather suit plans also contained a pouch for the collection of urine.
About the Codice Atlantico: Pompeo Leoni, a 16th century sculptor collected Leonadro da Vinci’s notebooks and drawings and bound them into a collection. The Codice Atlantico is a twelve-volume set of 1,119 pages dating from 1478 to 1519 and consists of all sorts of drawings attributed to da Vinci. The Codice is currently housed at the Biblioteca Ambrosiana, Milan.