100 Knots

The Pentagon is developing a super-fast submarine that will travel about four times the current speed limit:

The technology, if developed, could revolutionize ocean transportation if it could be adapted to cargo and passenger ships. The vehicle would travel inside a large gas bubble created in the water, a process known as supercavitation. The bubble reduces drag, since the drag is much lower in air than in water, allowing the vehicle to travel at high speeds.

(Hat tip: Like Cool)