Sam's a pretty famous cat, but unfortunately his story doesn't line up very well.
For starters, none of the surviving members of Bismarck recall a cat being on board, nor are there any photos of him on board (although it's possible there were and they went down with the ship).
Next is the fact that HMS Cossack was not actually one of the ships engaged in rescuing survivors from Bismarck so the chances of her spotting and then stopping to pick up a random cat in the middle of the ocean are relatively low.
Later on when he's supposed to be rescued from a sinking HMS Ark Royal, the ship sank pretty slowly producing little wreckage while most of the crew were evacuated in good order, so if he was bored he probably would have been evacuated with the rest of the crew during the relatively calm evacuation.
Lastly, there's the fact that there are two different versions of "Unsinkable Sam," with one instance of him being a black and white cat, and the other being a slightly chonkier tabby.
It's a fun story though, and explanations do exist for all those points, however unlikely. Cats on warships were actually pretty common so there are lots of kitties that have tales of there time in the war. If you'd like more info, I highly recommend the video "A Short History of Ships Cats - Floating Felines, Maritime Moggies and Kleptomaniac Kittens" by Drachinifel on YouTube.
For starters, none of the surviving members of Bismarck recall a cat being on board, nor are there any photos of him on board (although it's possible there were and they went down with the ship).
Next is the fact that HMS Cossack was not actually one of the ships engaged in rescuing survivors from Bismarck so the chances of her spotting and then stopping to pick up a random cat in the middle of the ocean are relatively low.
Later on when he's supposed to be rescued from a sinking HMS Ark Royal, the ship sank pretty slowly producing little wreckage while most of the crew were evacuated in good order, so if he was bored he probably would have been evacuated with the rest of the crew during the relatively calm evacuation.
Lastly, there's the fact that there are two different versions of "Unsinkable Sam," with one instance of him being a black and white cat, and the other being a slightly chonkier tabby.