While most DARPA projects never materialise, the Underwater Express mini-submarine project is entering the test phase. If successful, the Underwater Express will be capable of going 100 knots—far faster than the 30 knots today's subs can muster.
To achieve the amazing speeds, the sub utilises a hydrodynamic effect known as supercavitation. When the Underwater Express achieves enough speed, a gas bubble envelops the vessel and reduces drag allowing it to achieve speeds not otherwise possible—not unlike the USS Enterprise's warp field. The submarine's designer, Electric Boat, is working on a one-quarter scale model for sea trials off the coast of Rhode Island. If the trials are successful, Electric Boat will begin production on a full scale 30m submarine. Seals had better watch out, I doubt the Underwater Express will feel remorse as it rams into adorable marine life at 100 knots. Unlike the regular express where all you see is bums peeing on the wall, here you get to see sharks explode. [Popular Science]