The tap water on a modern cruise ship is 100% safe to drink and often higher in quality than the municipal water found in many cities. Cruise ships use advanced onboard treatment plants that utilize Reverse Osmosis and multi-stage distillation to turn seawater into pure, potable water. This water is then mineralized for taste and chlorinated to ensure it remains sterile in the ship's holding tanks. Cruise lines are held to incredibly strict "high-fidelity" standards regulated by the U.S. Public Health Service (USPHS) and the Vessel Sanitation Program (VSP), which conduct unannounced inspections and frequent laboratory testing of the water supply. While the water from your cabin bathroom sink is perfectly safe, some guests prefer the taste of bottled water because the ship's water can occasionally have a faint "mineral" or "chlorine" aftertaste. However, for drinking, brushing your teeth, or making coffee, the ship’s tap water is a rigorously tested and safe resource that meets or exceeds World Health Organization standards.