Where does it go? The waste products from the toilet are actually consigned to a treatment plant in the bowels of the ship were it is purified before being pumped back into the ocean away from land. Raw sewage is not allowed to be discharged into the ocean.

Toilet waste on a modern ferry, often referred to as "black water," is managed through sophisticated onboard systems designed to meet strict international maritime environmental standards. Most large ferries utilize vacuum-flush toilets that pull waste into a central holding tank using very little water. Once collected, the waste is treated in an Advanced Wastewater Purification System (AWPS). This process involves biological treatment where bacteria break down organic matter, followed by filtration and disinfection (often using ultraviolet light) to kill pathogens. The resulting treated liquid is remarkably clean and can be legally discharged into the open sea while the vessel is moving, provided it is at least 12 nautical miles from land (or closer if the treatment is sufficiently advanced). Any remaining solid waste, known as "sludge," is stored in tanks and either incinerated at high temperatures on the ship or, more commonly, pumped out at a port's specialized "honey wagon" facility once the ferry docks. These regulations, governed by the International Maritime Organization (IMO), ensure that ferries do not contribute to coastal pollution, protecting the marine ecosystems they traverse.