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Designs for underwater boats date back to the 1500s. In the 19th century, the first useful submarines began to appear. During the Civil War, the Confederates built the H.L. Hunley, a submarine that sank a Union ship, the U.S.S. Housatonic, in 1864. But it wasn't until World War I that the first truly practical submarines emerged. Have you ever been on a submarine? Ask your family if they have and what it's like.
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进步时代
