What are fillable tanks used to provide additional weight to vessels called?

Ballast tanks are specifically designed to provide additional weight to vessels, enhancing their stability, balance, and handling in the water. By taking on water, these tanks lower the center of gravity of the ship, making it less prone to capsizing and improving its overall performance, particularly in rough seas. Ballast tanks can often be filled or emptied depending on the vessel's operational requirements, allowing for adjustments to weight distribution as needed during various phases of a journey.

Air tanks, water tanks, and service tanks serve different purposes. Air tanks manage air pressure for various systems, water tanks typically store fresh water for crew use, and service tanks might hold fuel or other operational fluids. Each of these tanks plays a critical role in the overall operation of a vessel, but none fulfill the primary purpose of adding weight for stability as ballast tanks do.