St. Sebastian was built as a private motorboat of the same name by Captain R. D. Hardee at St. Sebastian, Florida. On 25 June 1917, the U.S. Navy acquired her from her owner, J. W. Taylor of Marathon, Florida, for use as a section patrol vessel during World War I. She was commissioned as USS St. Sebastian (SP-470) on 9 August 1917.
St. Sebastian operated on patrol duty in Florida waters for the rest of World War I and into early 1919. She was out of commission and awaiting sale when she became one of several section patrol boats destroyed at Key West, Florida, on 9 September 1919 by the Florida Keys Hurricane.
Sources vary as to when St. Sebastian was stricken from the Navy List. It may have occurred on 24 April 1919 in advance of her being put up for sale or on 4 October 1919 after her destruction.