Geriaviator, I've just discovered the answer to my own question re the Castle Archdale picture that you posted. I found it at Wikki (where else?) which says:-
Sunderland and Catalina flying boats of RAF Coastal Command at Castle Archdale in Northern Ireland, January 1945.
The big freeze. Nearly all the aircraft on strength with three Coastal Command squadrons are visible here, drawn up out of the water at Castle Archdale in Northern Ireland as Logh Erne froze over in January 1945. More than 30 aircraft can be seen, including Sunderlands of No's 201 and 423 RCAF Squadrons and No 202 Squadron's Catalinas.
here:-
File:Sunderland and Catalina flying boats of RAF Coastal Command at Castle Archdale in Northern Ireland, January 1945. CH14837.jpg - Wikipedia, the free encyclopedia
One of the disadvantages of flying from a fresh water rather than sea water base, I guess. I recall a fellow pilot on 30 Squadron who had once flown Sunderlands, of which he spoke most fondly. He said that you needed to have as much Seamanship as Airmanship to operate them properly.