How did peoples benefit from submarine

This is not technically English unless you were making the definition of what people used it for but anyways, here is what Submarines are used for:

1. They are used for tourist to look underwater and see aqua nature and to see various things that organisms do underwater. I hear its popular in tropical areas such as Hawaii 

2. They along with slight variations of underwater craft are used by scientist to do deep underwater to find and study deep underwater organisms since submarines are resistant to a lot of water pressure

3. They are used by navies from around the world in naval warfare, they became well known in the World Wars because they were used by the Germans (aka U-boats) to sink ally ships in which they sunk the ship going to Liverpool which carried over 120 passengers from America which sparked Americans to stand together and declare war on the Germans in World War 1.

They advanced in warfare and were able to explore the depths of the ocean.

Hope this helps can please put this as brainliest answer