A screw steamer or screw steamship is a steamship or steamboat, powered by a steam engine, using one or more propellors, also known as screws, to propel it through the water.The term is usually used in contradistinction to the paddle steamer, an earlier form of steamship that was largely, but not entirely, superseded by the screw steamer.The screw or propeller was first developed by Swedish inventor John Ericsson for the U.S. Navy.