Why two coastal ironclads might achieve nothing

Would a Confederate casemate ironclad fighting a large monitor in coastal waters make an interesting battle?

Probably not; they could pound each other for hours without achieving much.

A viewer proposes matching a Confederate casemate ironclad with a large monitor in a coastal seaway. The reply expects a long exchange of fire rather than a decisive tactical contest. Hours of pounding could leave both ships still in action, with no meaningful result. The example is a stalemate in which neither side can quickly overcome the other's protection.