Sinking ships; exploring the depths.
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.
The Germans were the first to use Submarines in World War 1. Now i believe that the marines now do at times.
For eating ;)
Yes, they did.
The early SS and the newer GATO Class diesel submarines.
Depth charges.
military submarines use low frequency antenna that extends from the sail(conning tower.) The message is typed into a computer, then is sent to another submarines antenna that receives it and displays it on a computer.
Submarines use echolocation to detect, locate, and avoid obstacles underwater, as well as to navigate their surroundings. By emitting sound waves and analyzing the echoes that bounce off objects, submarines can map their environment in conditions where visual navigation is limited or impossible.