The Rio de Janeiro Maru was a passenger/cargo vessel (total of 1,140 passengers) used on the Japan, Hong Kong, Singapore, South Africa, South America, Panama canal, US West Coast and back to Japan. Rio de Janeiro Maru appears to have been hit during the first attacks of 17 February 1944, possibly by planes from USS Yorktown and USS Bunker Hill. It is likely that she sank overnight. Today, the Rio de Janeiro Maru sits at a maximum depth of about 34 meters, with the ship lying on its starboard side. It is located on the eastern side of Uman Island, perhaps a few hundred meters off the southern most end. As visitors swim down onto the wreck it is quickly obvious that this is a huge wreck, the fourth biggest in Chuuk Lagoon in terms of tonnage. Dive boats generally anchor on the bridge area or near the bow. One of the first things tourists can see is the degaussing coils which were installed when she was taken over by the Navy. These coils are huge steel cables wrapped around the ship's hull just below the waterline that were an important part of any ship used in a theatre of war.