The first human torpedo was produced by the Italian navy in 1918. The curious craft driven by Lieutenant Raffaele Rossetti and Lieutenant Raffaele Paulucci was based on a submarine torpedo and was propelled by compressed air. The two pilots sat with their heads out of the water and were extremely vulnerable. Despite this, the craft was used successfully to blow up the Austrian battleship Viribus Unitis as well as a German troop carrier.
These craft were never intended for suicide missions, as the name suggests, but were used for covert operations, allowing penetration deep into defended enemy harbours in order to attach explosives to warships.
Later, pilots wore a Belloni diving suit and rebreather apparatus allowing them to stay underwater for up to six hours. These ingenious suits also prevented tell-tale bubbles escaping to the surface, thus helping the pilots to escape detection. Image courtesy of the Italian Navy.