Queen Mary, an uncertain submarine claim, and Curacoa

Did Queen Mary sink a submarine?

The answer only tentatively recalls a possible ramming. It is definite about Queen Mary sinking the British cruiser Curacoa.

The suggestion that Queen Mary rammed a submarine receives only a tentative answer. The definite example offered is the British cruiser Curacoa, which the liner sank in a collision. The distinction matters because the recalled submarine encounter is left unconfirmed.