A crash dive is a maneuver performed by a submarine to submerge as quickly as possible to avoid attack. A submarine is a Watercraft that can operate independently below water as distinct from a Submersible that has only limited underwater capability Crash diving from the surface to avoid attack has been largely rendered obsolete with the advent of nuclear-powered submarines as they operate constantly submerged and are unlikely to be found on the surface. Nuclear power is any Nuclear technology designed to extract usable Energy from atomic nuclei via controlled Nuclear reactions However, the crash dive is a standard maneuver used during surfacing when a collision is believed imminent.

A crash dive in a diesel-powered submarine requires careful orchestration of the crew. Diesel or Diesel fuel (ˈdiːzəl in general is any Fuel used in Diesel engines The most common is a specific fractional distillate of petroleum On German U-boats of World War II, a crash dive would begin with the Captain or senior lookouts giving the order "Alarm!", which led to the Chief Engineer activating the alarm bell. Germany, officially the Federal Republic of Germany ( ˈbʊndəsʁepuˌbliːk ˈdɔʏtʃlant is a Country in Central Europe. U-boat is the anglicized version of the German word, itself an abbreviation of Unterseeboot ( undersea boat) and refers World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including See also Seafarer's professions and ranks A Chief Engineer is a Licensed mariner in charge of the Engineering department on a Merchant vessel All crewmembers would then immediately stop what they were doing and proceed to their diving stations. The crew would continue by flooding the forward ballast tanks of the submarine and, often, by having all available crewmembers move as far forward in the boat as practical (a "trim party"). This extra weight forward gives the ship a bow-down angle so its momentum helps pull it below the surface. A few seconds later the rear ballast tanks are flooded before the ship ends up with its stern rising out of the water. (An accident during the first patrol of U-505 caused just that when she crash dived to avoid an aircraft. Fortunately for the crew they weren't spotted while they got her back under control. The crewman who started flooding the rear ballast tanks late was subsequently given the nickname "Ostrich". The Ostrich ( Struthio camelus) is a large Flightless bird native to Africa (and formerly the Middle East) ) The entire operation would generally be coordinated by the Chief Engineer.

Before the hatches and air induction vents fall below the surface they must be closed. Before that, the diesel engines must be stopped or they will suck the air out of the ship in a matter of seconds. On submarines with direct drive, the engines are disengaged from the propeller shafts and the electric propulsion motors/generators are switched to motor mode. The motors are run at high speed to maintain the forward momentum. Once all the hatches and induction vents are closed the diving planes are used like the control surfaces of an airplane to pull the ship below the surface and level-out at the desired depth. In a World War II-era boat, the whole operation could take as little as about 30 seconds with a well-trained and experienced crew. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including In contrast, an Ohio-class ballistic-missile submarine may take as long as five minutes to reach periscope depth from the surface. History The first eight Ohio -class submarines were originally equipped with 24 Trident-I (C4 Submarine-launched ballistic missiles Beginning with

In extreme emergencies submarines have had to crash dive so quickly that lookouts were left on-deck. Such was the only survivor of U-68 when the four lookouts were left top-side as she crash dived among exploding aerial bombs. Commander Howard Gilmore earned the Medal of Honor during World War II by ordering a crash dive ("Take her down!") while wounded and unable to leave the bridge of USS Growler (SS-215). Howard Walter Gilmore (September 29 1902 – February 7 1943 was a Submarine commander in the United States Navy who was awarded the Medal of Honor posthumously The Medal of Honor is the highest military decoration awarded by the United States government. World War II, or the Second World War, (often abbreviated WWII) was a global military conflict which involved a majority of the world's nations, including First patrol (June - July 1942 Growler ’s first war patrol began 29 June 1942 as she cleared Pearl Harbor for her assigned patrol area around Dutch