Liquids are great at absorbing bullets' energy. Fired underwater, an AK-47 can only send a bullet a few feet forwards, while in the air the same bullets would easily fly over 1,000 feet. This is great news for secret agents looking to avoid henchmen by swimming underwater, but it's impractical advice for anyone else unless they want to carry six-foot-thick tanks of water around themselves at all times. Fortunately, researchers have found liquids that work even better than water at stopping bullets. The latest, developed by Poland's Military Institute of Armament Technology in Warsaw, is a new non-Newtonian Shear Thickening Fluid, and it might replace Kevlar in body armor of the future.