Abstract: Auxiliary flotation apparatus to provide supplemental flotation for a vessel which may be in danger of sinking. The apparatus is a self-contained cannister capable of being connected to a source of pressurized air. To assure stability of the disabled vessel, two or more of the cannisters would preferably be mounted at an outboard end to each side of the hull of the vessel at spaced locations below the water line. Should the need arise, the source of pressurized air can be manually or automatically activated for introduction into the cannister. In response to the pressurized air, a projectile is propelled in a direction away from the vessel and caused to rupture a frangible membrane located substantially flush with the hull of the vessel. The projectile proceeds far beyond the vessel and draws with it an attached inflatable tubular sheath of flexible, air impermeable sheet material.