Graham Hawkes is building the DeepFlight Super Falcon, which is a cross between a submarine and an airplane. Its a sub, obviously, but it "flies" underwater, using aircraft type control surfaces, etc.
He has a goal to actually do a loop (loop upside-down) in Lake Tahoe soon. This will apparently be a first for a submarine.
Fox News has an interview with Hawkes where they discuss the craft a bit.