HMAS Diamantina (K377) deepest known part of the Indian Ocean on 7 February 1960, which was named Diamantina Deep after the ship. Based in Fremantle, Western Australia, "Diamantina" remained in service as an oceanographic vessel until 1980; she briefly interrupted these duties in March 1963, escorting the royal yacht during Queen Elizabeth II's tour to Australia. "Diamantina" paid off from the RAN on 29 February 1980, and was the last World War II-era frigate to serve Australia. "Diamantina" was handed over to the Queensland Maritime Museum to be permanently berthed in the South Brisbane Dry Dock located on the Brisbane River at South
Mariana Trench Mariana Trench The Mariana Trench or Marianas Trench is located in the western Pacific Ocean approximately east of the Mariana Islands, and has the deepest natural point in the world. It is a crescent-shaped trough in the Earth's crust averaging about long and wide. The maximum known depth is (± ) at the southern end of a small slot-shaped valley in its floor known as the Challenger Deep. However, some unrepeated measurements place the deepest portion at . For comparison: if Mount Everest were dropped into the trench at this point, its peak would still be over under water. At