A research project on development of observation systems for heat, momentum and substance circulation in the ocean and atmosphere was carried out in the Research Institute for Applied Mechanics, Kyushu University from 1992 to 1997. A pitch, roll and depth controllable towed vehicle called "Flying Fish" was developed, which houses an acoustic Doppler current profiler (ADCP), CO2 analyzer and sensors for measuring temperature, salinity, dissolved oxygen, pH, turbidity and chlorophyll. Length of the vehicle is 3.84m, breadth 2.26m, height 1.4m, weight in air 1300kg and weight in water about 0kg. Flying Fish enables us to obtain space continuous data on physical and chemical properties efficiently in the upper mixed layer of the ocean. From 1994 to 1997, the vehicle was used to carry out ocean observations in the northern, southern and central part of the Japan Sea in a collaborative study among Japan, Korea and Russia. Examples of data obtained are shown in this paper and the results of the current velocities are compared with those of other observation systems.