Magnet was built as a private motor yacht of the same name by the Electric Launch Company at Bayonne, New Jersey, in 1910. On 11 June 1917, the U.S. Navy acquired her from her owner, H. F. Lippett, for use as a section patrol craft during World War I. She was commissioned as USS Magnet (SP-563) on 27 June 1917. Magnet served on patrol duties for the rest of World War I. She was ordered sold on 1 October 1919 and was sold in 1920.