she stopped at Hampton Roads, Tampa, Florida, and Guantanamo Bay, Cuba. Consequently, the warship did not transit the canal until 25 October. She reached San Diego on 8 November and went back into the Rotating Reserve on 19 December. The warship returned to active duty in May 1935, and resumed operations along the west coast as a unit of DesDiv 19. Late in April 1936, she steamed south to the Panama Canal where she again joined in the maneuvers associated with the annual fleet concentrations which were conducted on the Pacific side of the isthmus. She returned to San Diego at the end of the first week in June and conducted normal operations for a month before leaving the west coast on 6 July. Her voyage to Hawaii came as a result of DesDiv 19's assignment to the Submarine Force in conjunction with sonar tests. Sometime during the first half of the year, Waters and her sisters in the division had received the latest sound gear—high frequency directional sonar which allowed a destroyer to locate a submarine more accurately. Previously, sonar could at best indicate the presence of a submarine somewhere near the destroyer. The new equipment enabled submarine hunters to estimate the interloper's bearing and distance and therefore increased the probability of success of the destroyer's depth charge attacks. From July 1936 until late June 1939, Waters and her division mates cooperated with units of the Submarine Force in experiments to develop the techniques which translated the theoretical potential of the new technological developments into efficient antisubmarine warfare doctrine. Waters departed Hawaii for the west coast on 20 June 1939. She reached San Diego ten days later and was assigned to the Underwater Sound Training School. Between that time and America's entry into World War II, the destroyer continued to develop the Navy's antisubmarine warfare capability by teaching techniques which she had developed to sonar operators and officers assigned to the Fleet. World War II When the Japanese launched their surprise attack on Pearl Harbor, Waters was in port at San Diego and still operating with the Sound School. She received word of the hostilities at 11:25 and immediately began preparations to put to sea. That afternoon, the destroyer made a three-hour antisubmarine sweep of the approaches to San Diego. On 8 December, she departed San Diego in the screen of Hawaii-bound aircraft carrier . Six days later, the