It is necessary to make use of the Okino Torishima in order to secure Japanese exclusive economic waters. A circle that is drawn with a radius of 200 nautical miles by making the island as the center covers 400,000 km2, which is approximately equal to the land area of Japan. We need to develop a beachhead for economic activities here so that the island may be fully recognized across the world as a base point of Japanese exclusive economic waters. To this end, it is urgently necessary to develop the technology for securing safe facilities by knowing the real conditions of ocean waves and tidal currents.

It is essentially inevitable that professional divers working in such a harsh environment as under the sea are exclusively devoted to operation efficiency and that they tend to forget to care about the environment of the sea. Training that is devoted only to skills is also responsible for nurturing divers who show no interest in the destruction of the marine natural environment even though they work in the sea.

Tuna once completely disappeared from the Tsugaru Strait where fishermen had enjoyed bumper catches before. But, the tuna fishing has been reviving and enriching the life of the neighboring fishermen since a couple of years ago in the Tsugaru Strait, especially at Oma. Why then was the tuna population dwindling in the strait for over twenty years? I consider this phenomenon to be tied to the progress of the Seikan Tunnel.