How does a Ballast Work?

The answer to this depends on what type of ballast your talking about. What immediately comes to mind for me is a water ballast, which is used in marine vessels to create steadiness or in the case of submarines allow the vessel to dive beneath the waves. Ballasts, in their most common usage can be considered as open tanks lining the hull of a ship, these tanks allow the kinetic energy of the waves to flow through the ship, instead of under and around it. Some ballast tanks may have the ability to pump water in and be flooded weighing the vessel down so it may dive beneath the waves.