Sorry to have to interrupt, but the PBY-5A WAS the amphibian version of the Catalina, and in fact many PBY-5A's still survive today precisely BECAUSE they were amphibious, that is they did not have to alight on the sea or a lake if a "land" airfield was available in the vicinity. Operating aircraft off water (salt or fresh) always seems to have been more hazardous than using an airfield (for various reasons), and operating off salt water usually guarantees a shorter life for any aircraft made of metal, or containing metal parts. A good way of obtaining an idea of how pilots were trained to fly this type of aircraft (and broadly applicable to many other larger-sized flying boats) would be to obtain a copy of the RAF Pilots' notes for the type (or an equivalent US Navy booklet). Perhaps other forumites might like to suggest where such publications might be obtained for a reasonable price.
David D