diving into the area below the bay, nhk world wataru sumida decided to find out. >> i'm about 10 meters under water off the coast. take a look over here. some of them are five meters wide and weigh about 60 pounds each. persistent efforts have opinion made. for example, this small black spikey thing is a sea urchin. >> this was about 50 meters from here and all you can see are sea urchins. experts believe it. and the seaweed destroyining th habitat of utter marine creatures. to restore the marine life which provides the region's famous food. >>> one of the marine creatures disappearing is a much prized seafood in japan. before the 2011 disaster they were a big money maker for local fishermen. today their numbers have plunged and while they're also a much loved food that's no comfort for fisheries. >> last month, local fishermen gathered for a meeting in n the city. their reports were not good. the hall of the local specialty was about one third of that before the tsunami. >> they would have been trying to clear the sea floor of urchins for five years now. on this day they caught more th