In 1998 and 1999, the Hydrography Department conducted comprehensive sea bottom surveys around Myōjin-shō, using the state-of-the-art survey vessel Shoyo and Manbou II, the second generation Manbou.
Manbou II conducted the survey of the sea area within a radius of 3 nautical miles (about 5.4 kilometers) of Myōjin-shō.