Hello Willy!
The "Ark Royal" you are thinking of was most probably the battleship "Royal Oak". Prien sunk this old battleship in Scapa Flow in 1939. The "Royal Oak" was put into service during WW1 but after several modifications it was still a danger for all German and Italian ships in the early days of WW2.
The other famous "Ark Royal" was built during the 1930īs and was sunk in 1941 by U-81 near Gibraltar. So the WW1 "Ark Royal" was a predecessor of this famous aircraft carrier.
Hope this helps!