Abstract: A container has an air tank therein occupying some of the space in the container. A projecting part extends from the container and has an open end coupled to the air tank via an air duct. A hole-filling member is mounted at the open end of the projecting part. A pump in the container selectively pumps sea water into the container and out of the container for maneuvering the container beneath the hull of a damaged sea vessel to position the hole-filling member of the projecting part in a hole in the bottom of the hull. Compressed air is supplied to the air tank to control the buoyance of the container and for expanding the hole-filling member in the hole in the hull to plug the hole.