In recent years, predictions of changes in the environment on earth and studies on ecodevelopment have become important. For this research on going ocean data in time and space is required, and has been obtainable using by mooring systems. However, a conventional mooring system can observe only discrete data in perpendicular space and moreover, construction of such a system requires a manpower and great expense. To solve this problem, an underwater vehicle for virtual mooring has been developed at Research Institute for Applied Mechanics (RIAM). The vehicle glides back and forth between the sea surface and the seabed collecting ocean data, with direction control regulating the vehicle's position in a designated area. This paper describes the testbed vehicle "LUNA" that was designed to develop a virtual mooring system, and the control algorithm is discussed.