It sounds like science-fiction, but there was actually a campaign called Project Rainbow with the goal of making a ship invisible to enemies. Project Rainbow is also known as the Philadelphia project, and, though denied by the government, is a popular conspiracy theory.
Though the story of what happened is very detailed, contradictions make the likelihood of it actually occurring a bit sketchy. In theory, the project relies on science discovered by Albert Einstein about electromagnetic radiation and gravity. Those who believe the navy succeeding in turning a ship invisible think that electrical generators were used to bend light and cause the ship to disappear from sight!
Carl Meredith Allen was the main promoter of the theory about invisibility. Some people later said that he had a long history of mental illness. However, his story got enough attention from US officials, which propagated the myth of the Philadelphia experiment even more.
Many of those who forwarded the story and added to its popularity relied on his proof and research. For this reason, many experts discount the theory. They also state other physical laws that make the scientific evidence cited by promoters of the theory null. What do you think: could we really use physics to make an entire ship disappear?