Submarines are vessels that can travel underwater. They can also float on the surface of the sea and move like any other ship.
Many submarines are powered by a nuclear reactor. The nuclear reactor creates extreme heat used to turn water into steam. The steam drives an engine that turns the propeller. The propeller pushes the submarine through the water.
Tanks on the sides of the submarine are filled with air or water. They allow the submarine to dive under water or surface on the water. Doors, called vents, on the top and bottom of each tank, open and close, letting in water or air.
While the submarine is on the surface, the tanks are filled with air. To dive, the vents are opened.
To make the submarine surface, the bottom vents are opened. The top vents remain shut. Air is pumped into the tanks to blow out the water. When the submarine reaches the surface again, all the vents are shut.
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