No, not really, submarines were first used successfully in the Civil War.
Atlantic Ocean.
Yes. Actually, the first submarines were used a number of years before 1912.
Revolutionary War 1776.
During WW2, all the major countries involved used submarines.
Germany made the first submarines in WW1. They were called U-Boats, short for "unterseeboat" Most modern submarines are descended from The Holland, christened in 1897, invented by John Holland.
Internal would be an adjective descrbing conflict, which would be a noun. The internal conflict is also a term used for a type of conflict in a story.
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.
Shallow diving submarines are used for reef watching in many parts of the world.
Nuclear energy is used to power most modern submarines
submarines were used in WW1 and the weapons used were torpedos and a deck gun.