On first appearances, this divers task seems a little daunting - as he pours a bucket of plankton into the gaping mouth of a whale shark that looks like it could swallow him whole. But despite its size, Hachibei, who at five metres is among the worlds largest and rarest species, is completely harmless. The shark is the latest visitor attraction at the Hakkeijima Sea Paradise Aquarium on the edge of Yokohama Bay in suburban Tokyo. The aquarium is one of the largest in Japan and is also home to an amusement park, including a rollercoaster which swings out over the ocean. The largest confirmed whale shark was 12.65 metres but it is thought they can grow to considerably greater lengths. The shark is found in tropical waters and lives for around 70 years. They feed mainly on plankton, microscopic plants and sometimes small fish. It has a cavernous mouth that can be up to 1.5 metres wide and contains between 300 and 350 rows of tiny teeth. The whale shark does not pose a significant danger to humans - and sometimes allow swimmers to hitch a ride. DM