A US Virginia-class attack submarine during sea trials in the Atlantic Ocean. Credit: US Navy courtesy of General Dynamics Electric Boat For over a century, the ocean has been the ultimate refuge for those who wished to disappear. From the U-boats of the first world war to the nuclear-powered leviathans that glide through today's deep waters, the submarine has thrived on one simple principle: stealth. Sound waves travel farther and faster in water than lig