Before joining the Atlantic Fleet "Delphy" tested submarine detection devices at New London, Connecticut, from 23 December to 31 December 1918 and aided survivors from "Northern Pacific", stranded off Fire Island, New York, on New Year's Day, 1919. "Delphy" sailed from New York on 13 January for winter maneuvers and torpedo practice in the Caribbean Sea. Returning to New York on 14 April with the Fleet, she sailed for Boston, Massachusetts, on the last day of the month for operations in preparation for the first transatlantic seaplane flight.