Milwaukee Deep at (), virtually identical with the "Milwaukee"s reading. The existence of deep water to the Atlantic Ocean side of the Caribbean has been known for more than a century. One of the area's earliest soundings was obtained June 12, 1852 by Lt. S. P. Lee, U.S. Navy brig "Dolphin", with a reading of at (). Milwaukee Deep Milwaukee Deep, also known as The Milwaukee Depth, () is the deepest part of the Atlantic Ocean and is part of the Puerto Rico Trench. It has a maximum depth of at least . It is just north of the coast of Puerto
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