A semi-submersible vessel comprising a plurality of stabilizing columns, a deck disposed between the tops of the columns, at least one void tank in one stabilizing column, at least one active variable ballast compartment disposed below the void tank, at least one emergency water ballast compartment disposed at the bottom of the stabilizing column below the active variable ballast compartment and below the void tank, wherein the emergency water ballast compartment is flooded during normal operating conditions, a pressurized air source for expelling water from the emergency ballast compartment, at least one control valve connected to the pressurized air source for rapidly passing air into the emergency water ballast compartment, and at least one port in the emergency water ballast compartment for expelling water from the emergency water ballast compartment.