Hm, that might be one of those cases of nautical terminology that 'floors' could be referred to as 'decks' regardless of whether you're on land or afloat. Not being a sailor, I wouldn't know.

It probably is the ship though. What year are we talking about? The battleship was broken up in 1949 and not even the navy would have two HMS Nelsons on the go at the same time.

Will you post the answer if you find out? It's intriguing.