It's a curious thing that as far as I know all the surviving Catalinas are the amphibious versions, leading people to believe that they were all designed like that, yet most of the versions used by the RAF and associated air forces during WW2 were true flying boats with no landing gear. This meant that to be able to beach them or bring them on land for maintenance the beaching gear had to be attached so they could be hauled out of the water.
Presumably for most of their operational lives they were moored in more or less salty water. Salt water + aluminium, not a good recipe for a long and happy life, and they were worked hard, with constant long patrols.
My father, who spent the war in Ceylon working on Catalinas after narrowly avoiding arriving in Singapore just as it fell to the Japanese, would tell me how they had to do all possible work on them while moored in a shallow lagoon, which meant getting on a boat. Some airmen would tie tools to themselves with string as if they dropped a crucial spanner into the lagoon they would get a proper bawling out from their NCOs. From time to time the best swimmers would be detailed to dive in and retrieve all these tools that had plopped into the lagoon.
A job that had to be done after each landing was to get aboard with a pocket full of tiny corks and look for any popped rivets in the hull, which could occur with a bumpy landing, and plug the holes. I imagine that they would all be re riveted when that aircraft came ashore for other major work.
The first time that my father and his fellow airmen there saw an amphibious PBY 5A it was a bit dramatic. They were used to seeing flying boats come and go on the lagoon but this one came round heading for the small airstrip. Expecting a terrible pile up some of them ran to the runway, wondering if it had sustained some damage that meant it couldn't land on the water. Miraculously, it sprouted wheels and came to a smooth landing. It aroused a lot of interest. They speculated that replacement Catalinas might all be like that. Apparently not.
The Americans were having enough problems of their own in the Pacific, so despite lend lease and all that, their most up to date aircraft were going to their own forces. Of course nobody knew that at the time, and information about anything was very limited. Most British servicemen in that area were more worried about a possible Japanese invasion of Ceylon as a stepping stone to British India after the catastrophic fall of Singapore and the loss of Malaya. It's hard to comprehend today how much of a blow the loss of the previously believed-to-be-impregnable fortress of Singapore was to the British psyche, and along with it the mythology of Western invincibility. What next? The Rock of Gibraltar, another near mythological icon dear to the British self image?
Anyhow, the Catalinas continued doing their thing until the end of the war.
There was a major cull of the non amphibious Catalinas after WW2 as the need for flying boats diminished, and the amphibious versions proved more versatile, with all the concrete airstrips that were built during and after the war.