. >> reporter: toyama bay is one of japan's richest fishing grounds.t has become known as nature's fish tank. water gushes up from the ocean floor. it's full of nutrients because it's fed by snow melt from the mountains surrounding the bay. the floor of the bay drops deeply to a depth of 1200 meters. that is another reason there are so many species of fish here. it's a great place for diving. akinoba kimura leads underground tours here and is keen to promote the toyama bay. >> translator: i think this is a perfect opportunity to promote the amazing ocean life here in toyama. >> reporter: recently kimura arranged a special event for a group of dive shop owners in the tokyo region. >> translator: do many of you lead night dive tours? >> reporter: kimura is confident there is a potential for night dive here because of the sea creatures. >> translator: this one you can only see late at night. >> reporter: it's late at night when they arrive at the bare shore. [ speaking foreign language ]. they dive into the darkness using underwater lights to see their wa