 On 7 May 1917, the U.S. Navy acquired her under a free lease from her owner, C. Chester Eaton of Brockton, Massachusetts, for use as a section patrol vessel during World War I. Enrolled in the Naval Coast Defense Reserve on 10 May 1917, she was commissioned as USS "Letter B" (SP-732) on 20 October 1917 at Norfolk, Virginia, with Quartermaster First Class L. C. Chamberlain, USNRF, in command.Assigned to the 5th Naval District, "Letter B" served as a harbor and shore patrol boat at Norfolk and Hampton Roads, Virginia, for the rest of World War I .She also served as a duty and emergency boat for seaplanes at Naval Air Station Norfolk.