Deep Navigation Colliery Deep Navigation Colliery Deep Navigation Colliery was a coal mine in South Wales, that operated from 1872 until 1991. Located next to the co-developed village of Treharris in the borough of Merthyr Tydfil, on development it was the deepest coalmine in South Wales Coalfield by some . Producing the highest quality steam coal, it powered both the Cunard passenger steamers RMS "Mauretania" and RMS "Lusitania" in their successful attempts at the Blue Riband prize for the most rapid Atlantic Ocean passage. The mine is also thought to have been one of several locally that provided coal to the RMS Titanic;
Challenger Deep of ± On 31 May 2009 the United States sent the "Nereus" hybrid remotely operated vehicle (HROV) to the Challenger Deep. Nereus thus became the first vehicle to reach the Mariana Trench since 1998 and the deepest-diving vehicle then in operation. Project manager and developer Andy Bowen heralded the achievement as "the start of a new era in ocean exploration". "Nereus", unlike "Kaikō", did not need to be powered or controlled by a cable connected to a ship on the ocean surface. "Nereus" spent over 10 hours at the bottom of the Challenger Deep and measured a depth of at