An autonomous underwater vehicle can move freely in the sea. These are used to explore marine resources, survey marine organisms, and monitor infrastructure facilities. In the future, with the development of the marine industry, the range of use is expected to expand further. To efficiently utilize the mobile underwater body, a system that can supply power in the sea without pulling it up from the sea is desired. We have proposed wireless power transfer with receiving power of3 kW, a maximum power transfer efficiency of about 80 %, and a degree of freedom of position of several meters.