What a Schwerer Gustav shell would do to a warship

How would different warships deal with a direct hit from a Schwerer Gustav railway-gun shell?

They probably would not survive the hit; the serious uncertainty is whether the railway gun could strike a moving ship at all.

A direct hit from Schwerer Gustav would be unsurvivable for the warships under discussion, whether the shell was high explosive or armour piercing. The projectile's enormous mass and energy make the precise filling less important once it actually strikes. The operational caveat is accuracy rather than destructive power. A railway gun able to engage a town or fixed fort still faces a much harder firing problem against a maneuvering ship. An immobile or anchored target might offer a chance, but the certainty of damage after a hit says nothing about the probability of achieving that hit.