 While "Halcyon" was under construction, the United States entered World War I on 6 April 1917.As a result, before "Halycon" could begin her intended fisheries service, the Bureau of Fisheries transferred her to the United States Navy on 14 May 1917 for war service.The Navy commissioned her the same day at Boston, Massachusetts, as USS "Halcyon" (SP-518), the first U.S. Navy ship of the name.