We describe an activity that is suitable for high school students and makes use of plastic bottles. This activity allows students to familiarize themselves with gas chemistry by introducing technologies that were applied in old submarine systems. Plastic bottles, which are representative of submarines, are used as reaction vessels. Three simple experiments regarding gas chemistry are carried out in the plastic bottles: (1) a carbon dioxide absorption reaction using soda lime, which mimics an air-cleaning canister; (2) a chlorine and hydrogen evolution reaction by the electrolysis of brine, which highlights the accidental generation of gases by lead batteries on board submarines; and (3) a catalytic hydrogen peroxide decomposition that exists in submarine propulsion system. To introduce an antisonar countermeasure system outside the submarine, a fourth experiment on hydrogen generation by the reaction of calcium hydride and water is also conducted.