Propane Tank Submarine
Three inventors from Kentucky, who are farmers by trade, came across old liquefied petroleum gas (LPG) storage tanks and wanted to put them to good use. So, they decided to turn them into a working submarine. The body structure is composed of two storage tanks, with the larger being the main body, while a section of the smaller one was welded to the top, thus creating a superstructure that provides headroom to occupants. Read more for a video of it in-action and a bonus.

No, you won’t find a massive engine, but rather several batteries that are not only used for propulsion, but also to power a hydraulic pump. The latter is used to drive the main propeller as well as to control the rudder and diving planes. A custom fabricated steel tray filled with concrete acts as a heavy keel to give the submarine neutral buoyancy and to keep it upright. To submerge, large blue ballast tanks can be flooded with water, while coming up to the surface requires compressed air cylinders mounted below to force the liquid back out.

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Bonus Video