I believe you are referring to Composite Submarines- a noun clause. a composite submarine has one parent sub- (that"s another question) launch a smaller assault or other submarine carried in tandem. the idea is somewhat similar to the Composite Bomber idea that was experimented with by the British in the interwar era- the Maia-Mercury Composite, for example- and the practical launch of a Space Shuttle- albeit a drop test- from a Boeing 747 as a lifting aircraft. the idea is similar- two subs superimposed, one of course having a longer range. I am not aware of any current USN activity in this field it is always possible. the Parent craft would have to be modified with hatches, etc. it is an intriguing idea. I believe some of the minisubs that were piloted by Sylvia Earle were launched submerged from regular subs- how this was done I am not sure, look her up! Good luck.
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.
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.
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.)
Submarines are still used by many navies to watch other navies ships and to protect coastlines secretly.