A diesel driven fully submerged hydrofoil catamaran has been completed. She is a newly developed passenger ferry with the speed of 40 knots and passenger capacity of 341 and now in commercial service on the Oki Islands route in Shimane Prefecture. Her technical features are as follows : (1) Catamaran hull brings hydrofoils with bigger span and small hull resistance in take-off condition and relatively soft wave impact in rough seas because of greater dead rise of the bottom than the mono-hull type. (2) Tandem foil configuration where fore and aft hydrofoils are exactly the same shape brings higher aspect ratio with high lift to drag ratio in comparison with the canard foil configuration on existing craft. (3) Automatic ride control system keeps foil-borne condition stable. (4) Her propulsion system consists of 4 sets of light weighted high-speed diesel engines and 2 sets of newly-developed light weighted water-jet propulsors.