Flying boats don't land on the water. They “alight”.
I had always believed that as well.
However I have a facsimile copy of the pilots notes for the Catalina, as published in Nov 1943, and "Promulgated by order of the Air Council" They relate specifically to the boat version - only a handful of the R.A.F's Catalinas were amphibians
It refers throughout to "landing".
An American aircraft, so perhaps it is one of many differences between English English and American English.