Why battleships carried underwater torpedo tubes

What was the point of fitting underwater torpedo tubes to a battleship?

They could discourage an enemy battleship from closing or finish a damaged ship, while an underwater mounting was safer than exposed deck tubes.

The torpedoes had two intended uses: deterring an enemy battleship from closing and finishing a damaged opponent when necessary. Mounting the weapons below the waterline also avoided some of the hazards of exposed deck-mounted torpedoes. They did not replace the main battery or become a battleship's principal striking arm. They were an auxiliary weapon meant to influence close-range choices and exploit an already favorable tactical situation.