At NAS Alameda, the early construction of the Seaplane Lagoon and two seaplane hangars before landplane hangars and the airfield reflected the importance of seaplanes and flying boats to naval air operations at the dawn of the Second World War. Though slower and less maneuverable than most land-based aircraft, they were essential for patrol, rescue, and transport missions because they could fly long distances over the ocean, land on water to recover downed aviators and sailors, and carry materials to places other aircraft could not reach. Between 1941 and 1960, a variety of seaplanes and flying boats operated there, beginning in January 1941 with seven Consolidated P2Y flying boats and the seaplane tender USS Pelican for training and operating flights. NAS Alameda also based Consolidated PB2Y-5 and PB2Y-5R Coronado aircraft, Scout Observation Units flying Vought OS2U Kingfishers, Curtiss SC-1 Seahawks with Scout Observation Service Unit Three, and Grumman J2F seaplanes used for rescue, ambulance, communication, and reconnaissance. In 1944, the P2Y aircraft were replaced by Consolidated PBY-5A Catalina flying boats, which joined forty-four Consolidated PB2Y-5 Coronado patrol bomber seaplanes in Transport Squadron VR-2; the Catalina became the Navy's most successful flying boat of the war, serving in patrols, search and rescue, and night attacks, while Coronados modified as PB2Y-5R transports carried passengers and cargo to Hawaii. Also arriving in 1944 were Martin PBM-3 and PBM-5 Mariner patrol bombers of Patrol Bombing Squadrons VPB-16 and VPB-145, some later modified into passenger transports, and these were eventually succeeded by Martin P5M Marlin flying boats, the last flying boat type stationed at NAS Alameda and the last used for U.S. naval operations before deactivation in 1967. Among the most prominent aircraft there was the Martin JRM-2 Mars of Transport Squadron VR-2, the Navy's largest flying boat: its prototype made seventy-eight trips between Alameda and Hawaii during the Second World War, and from 1946 to 1956 the JRM-2 averaged one flight per day to the Pacific, including Korean War service, carrying 214,000 passengers and more than 18,000 tons of cargo over ten years; five of the seven built after the prototype logged the equivalent of twenty round trips to the moon and set four world records, including carrying 301 servicemen from Alameda to San Diego in 1949. The Mars made its last Alameda flight in August 1956 and was replaced by the Consolidated R3Y Tradewind, which had equal carrying capacity and greater speed but suffered mechanical problems and several near disastrous crashes. During the 1950s, debris hazards in San Francisco Bay and the Navy's dedicated flying lanes, along with advances in land-based aviation, pushed military operations away from seaplanes and flying boats; in late August 1960, Patrol Squadron VP-47 departed NAS Alameda, ending twenty-nine years of flying boat service there, and in 1967 the Navy deactivated the seaplane base as part of the phase-out of the seaplane as a naval weapons system.