A submarine or submarine boat is a specialized watercraft that is designed to operate underwater to avoid detection and attack. Most major maritime navies of the world employ various types of submarines. Submarines are also used for marine and freshwater science and for engineering work at depths too great for standard divers.
Submarines encompass one of the largest ranges in capabilities of any vessel. They can range from small two man vessels that could examine the sea floor for few hours all the way to the largest submarines ever built which can remain submerged for months - sometimes even years - and carry enough nuclear missiles to destroy hundreds of cities in nations thousands of miles away.
Known as SSNs or SSs, depending on powerplant (though almost all in reality are nuclear powered SSNs), these are long ranged, high endurance hunter-killer submarines, designed to engage enemy shipping, tactical land targets and other submarines. These powerful boats are equipped with heavyweight torpedoes tubes capable of firing a wide variety of ordinance including torpedoes, UUVs and sub-launched SSMs, providing a large array of attacking options and proving the versatility of this warship type. More advanced designs also carry small VLS for sub-launched land-attack weapons.
Guided Missile Submarines
Guided Missile Submarines (SSGs or SSGNs) are enlarged attack submarines equipped with extensive facilities for launching cruise missiles against surface targets.
Ballistic Missile Submarines
These huge submarines (classified as SSBNs) are known as boomers or bombers, and carry large submarine launched inter-continental ballistic missiles designed to deliver various payloads against strategic enemy targets.
Coastal Patrol Submarines
Traditionally referred to as SSKs, these smaller submarines are designed for short-ranged coastal operations in defence of a nation's territorial waters, utilising their extremely quiet nature to ambush enemy vessels and submarines. These smaller vessels provide excellent ASW defence for the fraction of the cost of a larger and more complex SSN, and as such are popular in navies with tighter budgets and a defensive operational mandate.