Primarily the IJN & USN used subs for "battle." Reconnaissance and picking off special warships (flagships, carriers, etc.) was their mission. DKM primarily used their subs for merchant ship sinkings.
the battle of butthed island
The role of submarines during the second world war was primarily the destruction of enemy commerce, and occasionally heavy naval units such as battleships, cruisers, and aircraft carriers. Since the battle of the atlantic was fought primarily against German Submarines which were targeting Allied merchant vessels, there would have been very little point to using submarines.
Submarines typically use air tanks. Oxygen is very dangerous and very flammable. It's use is very limited on submarines for that reason.
submarines and bats both use sonar. Calvin was here
oceanographers use submarines to take pictures of sea life and things that have been found or things that they are looking for.
The marines do not use submarines. Only the Navy does.
Most submarines have propellers that spin, pushing them forward. A few smaller research submarines use a water jet for propulsion.
Submarines.
The Germans were the first to use Submarines in World War 1. Now i believe that the marines now do at times.
Sinking ships; exploring the depths.
Yes, they did.
For eating ;)