A submarine is used as a subsurface naval weapons platform, or as a tool of exploration and recreation. The latter may be manned or robotic, and have a wide range of characteristics and applications. They are usually operated from or with direct reliance on a support vessel of some kind. We've seen them carrying investigators to the deepest oceans, or surveying shipwrecks on the bottom of the sea.
The former are usually sophisticated naval vessels capable of great range and extended independent operation. They can carry torpedoes to sink other vessels, or guided missiles to be launched at distant targets to deliver nuclear payloads. The newer munitions include cruise missiles which can be launched from the submarine, or anti-ship missiles which can also be launched from below the surface. Certainly there are a number of instances of "spooks" working with the submarine service in a number of espionage or "black ops" projects. It could be the insertion of a SEAL team, or the gathering of intelligence in various ways.
During WW2, all the major countries involved used submarines.
They were used by submarines to navigate when not in open waters, They were also used by submarines and anti-submarine ships to locate enemy submarines.
Submarines todaee are used for underwater exploration,funn,new life underwater.
Nuclear energy is used to power most modern submarines
Shallow diving submarines are used for reef watching in many parts of the world.
submarines were used in WW1 and the weapons used were torpedos and a deck gun.
Both the Union and the Confederate had submarines, but the Confederate used them more often.
No, not really, submarines were first used successfully in the Civil War.
Yes, submarines were used by the Confederate Navy in the US Civil War.
World War I submarines were primarily used to locate and attack surface cargo and warships.
They are used for scientific research as well as warfare. Smaller submarines were used for scientific research (underwater animals, plants, etc.)
Britain, France, Germany, Italy and USA all used submarines during WW1