Where Do Cruise Ships Get Fresh Water?

Cruise ships make most of their own fresh water by turning seawater into drinking water, a process called desalination. A large ship surrounded by undrinkable ocean can produce hundreds of thousands of gallons of clean fresh water a day, more than enough for thousands of passengers and crew.

How desalination works

Ships use one of two main methods, and many carry both:

• Evaporation (flash distillation). Seawater is heated until it turns to vapor, leaving the salt behind. The vapor is then condensed back into pure fresh water. Ships often use waste heat from the engines to do this efficiently.
• Reverse osmosis. Seawater is forced under high pressure through fine membranes that block salt and impurities while letting water molecules through. This is the more modern, energy-efficient approach and is increasingly common on newer ships.

After desalination, the water is filtered, mineralized for taste, and disinfected before it reaches the taps.

Why ships make water instead of carrying it

A cruise ship uses an enormous amount of water every day — for cabins, kitchens, laundry, pools, and the crew. Carrying all of that from port would take up huge amounts of weight and space and tie the ship to frequent refills. Making water on board, using a resource the ship is literally floating in, is far more practical.

Ships do also load some water in port to supplement what they produce, especially before long stretches at sea, but onboard production handles the bulk of demand.

Storage and backup

Desalinated water is held in large onboard tanks so the ship always has a reserve. If the production plants ever go offline, those tanks and any port-loaded supply keep the ship running while the systems are restored. Strict health rules govern testing and treatment, so the water stays safe throughout.

Related guides

Part of our How Cruise Ships Work hub.