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Modern submarines, enormous ships that are self-contained wonders of technology, are able to produce oxygen and water for their occupants. They are equipped with their own power plants, and feature sophisticated food service, entertainment facilities, firefighting stations, and a place for worship. Ultimate Guide: Submarines demonstrates how the submarine has developed since its first appearance in the Revolutionary War . In addition, scientists are harnessing the power of submarine-like vehicles to investigate the depths of the oceans.