Leonardo da Vinci sketched his designs for scuba gear that would allow divers to breathe underwater and attack enemies from under their ships. Venice is surrounded by water, so it is very succeptible to attacks from enemies by ship. While Leonardo da Vinci was living there, he came up with the concept for soldiers to wear these underwater suits, which was a new category for war weapons. The suits were made with face masks to see, breathing tubes that were connected to a floating device for air, and ropes and other weapons can be carried along on the suit. His designs were carefully thought out, where they include metal pieces connecting the tubes to withstand high water pressure, and a pouch for unrine, since divers were anticipated to be submerged for a longer period of time. Picture source: British Library Online Gallery, Leonardo's diving apparatus design. http://www.bl.uk/onlinegallery/features/leonardo/diving.html