USN Float/Scout plane doctrine pre war was gunnery spotting, patrolling and scouting, during WWII shifted to patrolling, scouting and air sea rescue but largely superceded in the first two by land and/or carrier based types and also often in the final role. Accommodation for extra crew added weight, radar could replace second pair of eyes and allow searching in poor weather or at night. The increasing number of hostile aircraft likely to be encountered meant a performance boost was required. The age and size of the existing scout/observation fleet was also a factor.
Curtiss SOC Seagull, combined the scout and observation roles, built between September 1935 and August 1939, 162 mph seaplane, 168 mph landplane.
Vought OS2U Kingfisher pre war design, built between May 1940 and November 1942, 164 mph seaplane, 172 mph landplane.
Curtiss SO3C Seamew pre war design, built between April 1942 and January 1944, 167 mph seaplane, 182 mph landplane. Poor performance, many ended up as radio controlled targets, withdrawn in early 1944 favour of the earlier SOC.
Curtiss SC Seahawk, off the drawing board, probably thanks to the SO3C problems, contract for 500 signed 30 June 1943, another 450 added later, 384 cancelled on V-J day, first flight 16 February 1944, production in April 1944 to September 1945, delivered as land planes, 313 mph seaplane, 334 mph landplane. Another 9 SC-2 accepted September to November 1946 and a final one in March 1948, from a contract for 250 of which 240 cancelled V-J day, "new engine, modernised cockpit, one piece canopy, improved air sea rescue provisions."
The USN started receiving R-4 Helicopters as HNS in 1943, R-6 as HOS in 1945, the first USN order helicopters were the HO3S in November 1946, but only 6 built, along with 10 HTL, to end September 1947. If non carriers were going to have aircraft they had to be floatplanes for much of the 1945 to 1949 period.