Submarine explained to kids

A submarine is a watercraft that can operate underwater. It is typically used for military purposes, but it can also be used for civilian purposes, such as underwater research. The first submarines were designed in the early 1800s and they were used in warfare for the first time during the American Civil War. Submarines became a more important part of militaries during World War I, when they were used to sink enemy ships. Submarines were used extensively in World War II, and they remain an important part of militaries today. Most submarines are powered by nuclear reactors, which allow them to stay underwater for long periods of time. They typically have a crew of around 100 people. Submarines can be used for a variety of missions, including intelligence gathering, special operations, and research. They are also used to transport cargo and personnel.