Is it true that a reindeer was on a submarine in wwii?

The boat was the Royal Navy submarine HMS Trident (N52), and the reindeer doe was nicknamed Pollyanna. It was given to the Trident's Commanding Officer by a Russian Admiral as thanks for help that the British had given the Russians in 1941 in the Arctic.

Pollyanna lived aboard the Trident for several weeks unitl the boat returned to Portsmouth. Having gained weight along the trip, she could no longer easily fit through the hatch, so she was trussed by a local butcher and raised through the hatch with a winch.

She lived out her remaining days at a zoo, ironically dying within a few days of the Trident's decommissioning.