UNMANNED TRANS-SURFACE VEHICLE

A watercraft comprises a vehicle payload bay; a sail connected to the payload bay for propelling the watercraft in a foiling mode; and three or more hydrofoils connected to the payload bay. The hydrofoils are configured to provide control of the roll, pitch, and yaw of the watercraft and to elevate the vehicle payload by above a water surface when the watercraft is in the foiling mode. The hydrofoils can also provide control of roll, pitch, yaw, and elevation of the watercraft during the transition from a prone mode to a foiling mode. A mechanical propulsive system can be used for propelling the watercraft at least during transition from the prone mode to the foiling mode. The watercraft may not include a hull such that during the transition from the prone mode to the foiling mode, pitch and roll control are not substantially provided through the actions of gravity and buoyancy.