One MK48 strike.
OTH The FFG 7 class that was just recently used for target practice stayed afloat for over an hour after two mk48 hits( and numerous missile hits) and that was with no crew taking any DC action. The FFG class weighs maybe 5000 tonnes.
Here is FFG 43 floating after two mk 48 hits. No crew and no broken keel when clearly the after hit, below the flight deck was directly underneath the keel.
Things are different now.
Lucky shot. Lol.