No . A single hulled ship will sink no matter how thick the
outer armour is . The key to making the ship still float from
torpedoes is having an inner belt armour running from the front all
the way to the back. Bismarck's armour clearly demonstrated this .
The armour belt was completely intact . Even with torpedoes
explosion the belt didnt even have a dent on it. The reason why
Bismarck sank is becuz their crew blown the valves . This causes
the water to rush into the inner compartment.
And now i realize smth . U said the armour is 5 metres thick. Do
you have any idea of how thick is that? With that kind of armour ,
the ship can't even float. 
True , in the past , armour is depended on its
thickness , but its no where 5m thick.
