When ocean-going container ships unload some containers at a port of call, they must retain a balanced weight distribution throughout the vessel. To do this, they fill giant tanks of water that they have on either side, called "ballast water tanks", to compensate for uneven weight distribution.

However, ballast water picked up at one port could contain aquatic species that would be invasive at the next port if the ballast water were to be discharged there, causing ecological damage to the local environment. This has been the cause of many disturbances in the past.

Therefore, there are several regulations and best practices surrounding the management of ballast water on ocean-going vessels.