How a railgun projectile would damage ships and land targets

How would an electromagnetic railgun actually damage a ship or land target?

Its kinetic energy must be delivered along a useful path, with short-range side penetration and longer-range plunging fire producing different structural and flooding effects.

The anti-ship problem comes down to whether a projectile opens a path through which the sea can enter. A very fast round that passes cleanly through may achieve less than its energy figure suggests. At longer range, a ballistic arc can bring the projectile down through decks instead of straight through the side. The same kinetic energy would produce formidable land-attack effects, making trajectory and target construction as important as muzzle velocity.