A dry dock is a facility that removes a ship from its water environment. A dry dock can be dug out of the ground, such as a graving dock. It can also be a floating dry dock, that is, a vessel that is initially ballasted (weighted) down and can then lift a ship brought over it out of the water after deballasting. A heavylift ship also functions this way and will be discussed later. Dry docks have been pivotal throughout the history of both merchant marine commerce and naval sea power.