Currently top 10 attack submarines in the world are these: 
Nr.1 Seawolf class (USA) The boats of the Seawolf class are the most advanced but also the most expensive hunter-killer submarines in the world. These submarines were intended to restore the technological edge which the US Navy had enjoyed over the Soviets from 1945 until the mid 1980s, when espionage and the cynical trading practices of some US allies somewhat eroded it. The Seawolf class boats were intended to seek and destroy the latest Soviet ballistic missile submarines, such as Typhoon class, and latest attack submarines such as Akula class. Initially 12 boats of the class were planned. However these advanced submarines were too pricey even for the United States to build and maintain on the post-Cold War era budget. Eventually production was stopped with only three Seawolf class submarines built. All of these boats are currently in service. The US Navy switched to much cheaper design of Virginia class attack submarines. The Seawolf class submarines are arguably the quietest submarines in the world ever constructed. It is exceptionally quiet even at high speeds. Most submarines need to keep their speed down to as little as 5 knots to avoid detection by passive sonar arrays, while the Seawolf class are credited with being able to cruise at 20 kots and still be impossible to locate. A Seawolf at 25 knots makes less noise than an older Los Angeles classsubmarine tied up alongside the pier. These boats can operate at greater depths than existing US submarines and can also operate under the polar ice cap. Also these are faster than most other submarines. These submarines have eight 660 mm torpedo tubes. These tubes are used to launched Mk.48 torpedoes and Sub-Harpoon anti-ship missiles. Torpedo tubes are also used to launch Tomahawkland attack cruise missiles with a range of 1 700 km. A mix of 50 torpedoes, Sub Harpoons and Tomahawks can be carried. 
Nr.2 Virginia class (USA) The US Navy's Virginia class nuclear-powered attack submarines are successors to the Los Angeles class boats. The Virginia class was designed as smaller, less expensive and more versatile alternative to the advanced but extremely expensive Seawolf class. A total of 30 Virginia class nuclear-powered attack submarines are planned. The Virginia class submarines incorporate newly designed anechoic coating, isolated deck structures and new design of propulsor to achieve low acoustic signature. It is claimed that noise level of the Virginia is equal to that of the Seawolf class. The Virginia class submarines are fitted with 12 Vertical Launch System (VLS) tubes. These are used to launch Tomahawk land attack cruise missiles with a range of 1 700 km. Also there are four 533 mm torpedo tubes. These are used to fire a total of 26 Mk.48 heavyweight torpedoes and Sub-Harpoon anti-ship missiles. These boats can be also used for special operations. It is the first US submarine to employ a built-in Navy SEAL staging area allowing a team of 9 men to enter and leave the submarine. 
Nr.3 Astute class (United Kingdom) The first Astute class nuclear-powered attack submarine was commissioned with the Royal Navy in 2010. So far 7 boats of the class are planned. These will replace the older Swiftsure class attack submarines. The Astute class boats are significantly stealthies and carry more weapons than the previous boats ofTrafalgar class. These attack submarines are fitted with six 533 mm torpedo tubes. These are used to launch Spearfish torpedoes, Sub-Harpoon anti-ship missiles and Tomahawk cruise missiles. A mix of 36 missiles and torpedoes are carried. The Tomahawk Block IV land attack cruise missiles have a range of 1 700 km and can target enemy ships as well as land targets. 
Nr.4 Graney class (Russia) The Project 885 Yasen (Western designation Graney class) is the latest Russian nuclear-powered attack submarine. The lead boat, Severodvinsk, was laid down in 1993 however construction was stopped due to funding problems. This boat was commissioned with the Russian Navy only in 2013. The second boat of the class was built to improved project. Currently at least 6 of these boats are planned to be commissioned. These will replace the older Akula class submarines. Despite all improvements the Graney class boats are only slightly quieter than improved Akula class boats. The Severodvinsk has 24 vertical launch tubes for various cruise missiles. These include P-800 Oniks(Western designation SS-N-26), which has a range of around 300 km. Also there are eight 650 mm torpedo tubes. These can launch torpedoes and anti-ship missiles. It was reported that a mix of 30 torpedoes and anti-ship missiles are carried. The Severodvinsk has 24 vertical launch tubes for various cruise missiles. Cruise missiles include the P-800 Oniks (SS-N-26), which has a range of about 300 km. 
Nr.5 Sierra II class (Russia) The Russian expensive Sierra I class boats succeeded the ill-fated Alfa class. Soon even more capable Sierra II class boats were commissioned. The lead Sierra II class boat was commissioned in 1990 and the second boat of the class followed in 1993. Only two Sierra II class boats were ever commissioned due to extremely high price. The third boat was laid down, but was never commissioned and eventually scrapped. The Russian Navy maintains these advanced submarines despite their high operating costs. These boats have two light and strong titanium hulls. Soviet titanium technology was far in advance of the West, requiring fewer passes to achieve a successful weld, but the cost of the hulls limited the numbers built, despite advantages in depth and underwater speed. These submarines can operate at great depths. Their operational depth is 520 meters, while maximum depth is 750 meters. Most other attack submarines, such as Russian Akula class or American Virginia class operate at depths of only around 250 meters. Even the most advanced American Seawolf class boats can not dive that deep. 
Nr.6 Improved Los Angeles class (USA) The US Navy currently operates around 40 older Los Angeles class submarines alongside the newerSeawolf and Virginia class boats. These submarines proved to be an exceptionally good anti-submarine platform. First boat of the improved Los Angeles class was commissioned back in 1988. Improved submarines are much quieter than original Los Angeles class boats. It is described that improved Los Angles class boats are 7 times quieter than the original Los Angeles class boats. The class features a very potent weapon array, including Mk.48 torpedoes, Sub-Harpoon anti-ship missiles and Tomahawk land attack cruise missiles. The Tomahawk missile can be launched from the dedicated vertical launching system or from torpedo tubes. These boats can operate under ice where Russian ballistic missile submarines tend to hide. 
Nr.7 Akula class (Russia) In the late 1980s Soviet Union launched a number of Akula class boats. This clas marked a significant improvement in Soviet submarine design as it was far quieter than previous Soviet nuclear-powered attack boats. Fuerthermore the Akula class was far quieter than Western countries expected. The use of commercially available Western technology to reduce noise levels played and important role in this eroding a long-held NATO advantage in the underwater Cold War. Improved Akula II class boats became the first Soviet submarines that were actually quieter than the latest US attack submarines of that time, notably the improved Los Angeles class boats. Sensors were also much improved comparing with the previous Soviet attack submarines. These boats have four 650 mm torpedo tubes and four 533 mm tubes. Up to 40 torpedoes and missiles can be carried. Today Akula class boats make up about half or Russia's dwindling fleet to nuclear-powered attack submarines. 
Nr.8 Soryu class (Japan) The first Soryu class boat was commissioned with the Japanese Maritime Self-Defense Forces in 2009. Unlike other nuclear-powered boats on this list the Soryu class submarines have diesel-electric propulsion. These boats are fitted with air-independent propulsion system that allows to stay submerged for longer periods without surfacing to charge the batteries. Submerged endurance is increased from days to weeks. Japan is the only country to use this class of boats, as other diesel-electric submarines are intended for coastal and patrol operations. Air-independent propulsion system of the Soryu class enhanced stealth and operational capabilities of these boats. However these submarines lack range and endurance of nuclear powered attack submarines. Soryu class submarines have a hydrodynamic design and are fitted with anechoic coating. Loud components inside these boats also have sound insulation. Another drawback of these Japanese boats that these do not have a vertical launch system for anti-ship and land attack missiles. Their armament is limited to torpedoes and Sub-Harpoon anti-ship missiles, that are launched via torpedo tubes. 
Nr.9 Ohio class (USA) The Ohio class submarines were originally designed to carry intercontinental ballistic missiles and were classified as SSBNs. However between 2002 and 2008 the US Navy converted 4 of its oldest Ohio class submarines into cruise missiles carriers - SSGNs. Essentially its ballistic missiles were replaced by cruise missiles. Conversion of the first boat was completed in 2006. The Ohio, Michigan, Florida and Georgia were converted to guided missile submarines by replacing their Trident 2 intercontinental ballistic missiles with 7 smaller Tomahawk cruise missiles. Each converted SSGN is capable of carrying 154 Tomahawk cruise missiles. Such amount of cruise missiles is typically deployed in a surface battle group. Also these boats have four 533 mm torpedo tubes for Mk.48 torpedoes. Converted Ohio class submarines also have lockout chambers and can transport special forces personnel. 
Nr.10 Oscar II class (Russia) The Project 949A Antey boats, commonly known in the West as Oscar II class, are Soviet/Russian nuclear-powered cruise missile submarines (SSGNs). These are the third largest submarines ever built in terms of displacement and length. Only the Soviet Typhoon class and American Ohio classboats are larger. Also originally these were the largest attack submarines ever constructed. Currently these are among the most capable Russian submarines. Originally it was planned that 19 of these boats will be built. However only 11 boats were eventually completed. Currently 4 boats of this class remain in active service with the Russian Navy. By modern standards these boats are far from being stealthy. However these Russian submarines pack a formidable punch. Soviets designed these giant cruise missile boats to attack US aircraft carrier battle groups and coastal installations. The Oscar II class SSGNs are armed with 24 P-700 Granit (Western designation SS-N-19 Shipwreck) supersonic cruise missiles with a range of 550 km. These submarines are also fitted with two 650 mm and four 533 mm torpedo tubes, capable of launching both torpedoes and anti-ship missiles. These include the SS-N-16 Stallion anti-ship missiles with a range of 50 km, carrying torpedoes, nuclear warheads or nuclear depth charges for use against hostile ships or submarines. | 
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