The Rio DeJaneiro Maru was a passenger liner that originally provided service from Japan to South America before World War II. It was converted to a submarine depot ship during the war. It sank in Truk on February 17, 1944. The ship lies on it's starboard side at 110 feet. The bottom of the boat has created a spectacular coral reef covered with hard corals. Black and white dascyllus fish are seen profusely amongst the coral heads along with many other blue damselfishes. The cargo holds are stacked with crates of sake bottles.

The wreck has changed since I last visited the Rio in 2007. The superstructure is collapsing, making the entrance to the engine room much tighter. We followed our guide Madison into the darkness to see multiple gauges including 2 white faced engine room telegraphs. Multiple rifles were found hidden in the cargo hold along the top rim on the port side. The 6 inch stern gun is covered with hard stone corals. The propellers remain a spectacular site and provided refuge for a large school of bigeye trevally deep bellow the stern.