This article describes major accidents and incidents involving submarines and submersibles since 2000.

2000s 2000 Kursk explosion

In August 2000, the Russian Oscar II-class submarine sank in the Barents Sea when a leak of high-test peroxide in the forward torpedo room led to the detonation of a torpedo warhead, which in turn triggered the explosion of around half a dozen other warheads about two minutes later. This second explosion was equivalent to about 3–7 tons of TNT and was large enough to register on seismographs across Northern Europe. The explosion and the flooding by high pressure seawater killed the majority of the submarine's 118 sailors. Twenty-three survived in the stern of the submarine, but despite an international rescue effort, they died several days later either from a flash fire or suffocation due to a lack of oxygen. The Russian Navy was severely criticised in its home country by family members of the deceased crew for failure to accept international help promptly.

2001 Ehime Maru and USS Greeneville collision

On 9 February 2001, the American submarine accidentally struck and sank a Japanese high-school fisheries training ship, Ehime Maru, killing nine of the thirty-five people aboard, including four students, off the coast of Oahu. The collision occurred while members of the public were on board the submarine observing an emergency surface drill.

A naval inquiry found that the accident was the result of poorly executed sonar sweeps, an ineffective periscope search by the submarine's captain, Commander Scott Waddle, bad communication among the crew and distractions caused by the presence of the 16 civilian guests aboard the submarine.

The Navy and the command of Greeneville have been criticized for making no immediate attempt to help the Japanese on Ehime Maru that survived the initial collision. Weather conditions were producing waves and the submarine's partially surfaced condition prevented the opening of deck hatches. These were cited as reasons for the submarine captain's choosing to stand off and remain close by. While the U.S. Coast Guard directly responded, survivors resorted to automatically deployed life rafts from Ehime Maru.

2002 USS Dolphin major flooding and fire In May 2002, the U.S. Navy research submarine experienced severe flooding and fires off the coast of San Diego, California. The ship was abandoned by the crew and Navy civilian personnel, who were rescued by nearby naval vessels. No one was seriously injured. Although severely damaged, the boat was towed back to San Diego for overhaul.

USS Oklahoma City collision with tanker On 13 November 2002, collided with the Leif Hoegh liquefied natural gas tanker Norman Lady, east of the Strait of Gibraltar. No one on either vessel was hurt, and there were no leaks from fuel tanks and no threat to the environment, but the submarine sustained damage to her periscope and sail area, and put into La Maddalena, Sardinia, for repairs. Her commanding officer, Commander Richard Voter, was relieved of his command on 30 November. One other officer and two enlisted crew members were also disciplined for dereliction of duty.

HMS Trafalgar In November 2002, the Royal Navy's , , ran aground close to Skye, causing £5 million worth of damage to her hull and injuring three sailors. It was travelling below the surface at more than when Lieutenant-Commander Tim Green, a student in the Submarine Command Course, ordered a course change that took her onto the rocks at Fladda-chùain, a small but well-charted islet.

A report issued in May 2008 stated that tracing paper (used to protect navigational charts) had obscured vital data during a training exercise. Furthermore, the officer in charge of the training exercise had not been tracking the submarine's position using all the available equipment. Commanders Robert Fancy and Ian McGhie were court martialled and reprimanded over the incident.Royal Navy is condemned over crash of nuclear submarine, P&J, 23 May 2008

2003 HMAS Dechaineux flooding On 12 February 2003, , a of the Royal Australian Navy (RAN) was operating near her maximum safe diving depth off the coast of Western Australia when a seawater pipe burst. The high-pressure seawater flooded the lower engine room before the hose was sealed off. It was estimated that if the inflow had continued for another twenty seconds, the weight of the water would have prevented Dechaineux from returning to the surface. The Navy recalled all of the Collins-class submarines to the submarine base HMAS Stirling after this potentially catastrophic event, and after naval engineers were unable to find any flaws in the pipes that could have caused the burst, they commanded that the maximum safe depth of these submarines be reduced.

Great Wall 361 accident

In May 2003, China announced that the entire ship's crew (70 people) had been killed aboard the Ming-class Great Wall submarine 361 due to a mechanical malfunction. The accident took place off the coast of Liaoning province in northeast China. The vessel was recovered and towed to an unidentified port, where the cause of the accident was identified. When the battery was running low, the submarine surfaced with a vent opening for oxygen, which was consumed heavily by the charging diesel engines. At the same time, a sea wave surged, and seawater started to flow into the opening vent that automatically closed to prevent flooding. There was no single device on the submarine to detect low oxygen level and the crew suffocated due to the diesel engines consuming all the oxygen present within the submarine. As a consequence, the Commander and the Political Commissar of the People's Liberation Army Navy were dismissed from service, as well as the Commander, Political Commissar and Chief of Staff of the Northern Fleet.

K-159 sinking In August 2003, the Russian sank in the Barents Sea. This submarine had been decommissioned, and she was being towed away for scrapping. Of her skeleton crew of ten sailors, nine were killed.

USS Hartford grounding

On 25 October 2003, the American ran aground in the harbor of La Maddalena, Sardinia, in the Mediterranean Sea. This grounding caused about nine million dollars' worth of damage to Hartford.

2004 HMCS Chicoutimi fire On 5 October 2004, the Canadian submarine suffered from two fires after leaving Faslane harbour for Halifax harbour. One officer, Canadian Forces Lieutenant(N) Chris Saunders, died the following day while he was being flown via helicopter to a hospital in Ireland. Canadian Forces investigators concluded that poor insulation of some power cables caused the fires. The following board of inquiry found that the fire was caused by a series of events that caused electrical arcing at cable joints from seawater penetration at the joints.

2005 USS San Francisco collision with undersea terrain On 8 January 2005, the , while underway and submerged, collided with a seamount about south of Guam in the Marianas Islands. One of her sailors, Machinist mate 2nd Class (MM2(SS)) Joseph Allen Ashley, of Akron, Ohio, died from the injuries he suffered in the collision. This happened while San Francisco was on a high-speed voyage to visit Brisbane, Australia.

An additional 97 sailors were injured in this accident, including two with dislocated shoulders. navy.mil], NNS050509-14 – USS San Francisco Investigation Completed The collision with the seamount was so severe that San Francisco nearly sank. Accounts from the scene related a desperate struggle for positive buoyancy after her forward ballast tanks had been ruptured. Several news web sites stated that the boat had hit an "uncharted seamount" at a high speed. Commander Kevin Mooney was relieved of command of the San Francisco after an investigation revealed that he had been using inadequate methods of ocean voyage planning.

San Francisco underwent a rapid deceleration from more than to a standstill, causing a section of her bow to collapse (including her sonar system along with the forward ballast tanks) and everything not tied down to fly forward in the boat. San Francisco returned to her base at Guam, where emergency repairs were carried out. Next, she steamed to the Puget Sound Naval Shipyard for more permanent repairs. The bow section of San Francisco was replaced with that of a sister ship, , which had already been removed from service because of years of wear and tear.US Navy. USS Honolulu Holds Final Change of Command Ceremony . 14 December 2006.Nose of USS Honolulu to go to USS San Francisco The Honolulu Advertiser This replacement of the bow of San Francisco was successful, and the vessel returned to active service in the Pacific Fleet, based at San Diego.

AS-28 emergency

On 5 August 2005, the Russian AS-28, while operating off the coast of the Kamchatka Peninsula, became entangled in a fishing net, or possibly by cables belonging to an underwater antenna assembly, at a depth of . Unable to free itself, the submarine was stuck with a depleting air supply.

After a multi-national effort, a British Royal Navy team using a Scorpio ROV was able to free the submarine from the entanglement, allowing it to return to the surface. All seven crew members were rescued safely.

USS Philadelphia collision with MV Yasa Aysen On 5 September 2005, was in the Persian Gulf about northeast of Bahrain when she collided with the Turkish merchant ship MV Yasa Aysen. No injuries were reported on either vessel. The damage to the submarine was described as "superficial." The Turkish ship suffered minor damage to its hull just above her waterline, but the United States Coast Guard inspected the ship and found her to be still seaworthy. The commanding officer of Philadelphia, Commander Steven M. Oxholm, was relieved of his command following this collision.

2006 Daniil Moskovsky fire On 6 September 2006, the Russian Victor III-class submarine Daniil Moskovsky suffered a fire which resulted in the deaths of two crewmen (a warrant officer and a sailor). At the time of the incident the submarine was anchored off the Rybachiy peninsula, on Russia's north coast near the border with Norway. The fire was extinguished with no damage to the reactor (which had been scrammed as a precaution), and the submarine was towed to a base at Vidyayevo. The incident was reported as being caused by an electrical fire in the vessel's wiring.

USS Minneapolis-Saint Paul incident Four crew members were washed overboard from by heavy waves on 29 December 2006 in Plymouth Sound, England. This resulted in the deaths of Senior Chief Thomas Higgins (chief of the boat) and Sonar Technician 2nd Class Michael Holtz. After the preliminary investigation, Commander Edwin Ruff received a punitive letter of reprimand, stating that the accident was avoidable, and he was reassigned to a shore-based post in Norfolk, Virginia.

2007 USS Newport News collision with Japanese tanker Mogamigawa On 8 January 2007, was transiting submerged in the Strait of Hormuz when she hit the Japanese tanker Mogamigawa.U.S. sub collides with Japan ship, CNN, 8 January 2007 She had been operating as part of Carrier Strike Group 8 (CSG-8), organised around the aircraft carrier and dispatched to the Indian Ocean to help support operations in Somalia.

HMS Tireless On 21 March 2007, two crew members of the Royal Navy's , were killed in an explosion caused by air-purification equipment in the forward section of the submarine. The submarine was in service in the Arctic Ocean and had to make an emergency surface through the pack ice. A third crewmember who suffered "non-life-threatening" injuries was airlifted to a military hospital at Elmendorf Air Force Base near Anchorage, Alaska. According to the Royal Navy, the accident did not affect the ship's nuclear reactor, and the ship sustained only superficial damage.

2008 HMS Superb collision