DARPA is seeking concepts for an aircraft that can clandestinely insert and extract an eight-person special-forces team. The mission is to take off from a runway, fly 1,000nm as a conventional aircraft, fly another 100nm close to the surface, then travel the final 12nm to the coast underwater. Transit should take less than 8 hours, including any time required to land on water and reconfigure from aircraft to submarine - and the vehicle should be able to loiter near the coastline - on or under the surface - for three days in sea state 5. Then return the same way...