1The navy's new submarine is equipped with advanced sonar technology for detecting enemy ships.
2Scientists are using a submarine to explore the deepest parts of the ocean and study marine life.
3The submarine was launched from a naval base and sailed undetected through enemy waters.
4The crew of the submarine had to be rescued after it experienced mechanical failure and was unable to surface.
5The discovery of a World War II submarine off the coast of Japan has shed new light on the country's naval history.