On a small vessel like a destroyer or corvette they don't have turrets, they have mounts. A mount is attached to the deck under it while a turret extends down several decks, perhaps to the keel. When the turret turns the whole aiming system and magazine turn with it. When it fires the recoil gets absorbed by the decks of the whole vessel through which it passes. A gun mount transfers all recoil energy directly to the deck. For a small bore weapon that's acceptable. But for a 16" dia rifle accelerating a half-ton shell down it ... you need a turret.

A turret will fall out of a capsized vessel.