The S.S. United States began to be flooded at about 20:40 Dutch time in the Gulf of Mexico off the coast of Florida, in a planned effort to turn the retired passenger ship into what proponents hope will become the world’s largest artificial reef and a popular diving attraction. The sinking was expected to take several hours. Opponents wanted the vessel preserved as a historical monument, but their legal objections were rejected. Loose objects and hazardous substances and materials had been removed beforehand, and the upper deck is intended to lie about 18 metres below the surface.

The ship had been withdrawn from service in 1969 and had been docked in Mobile, Alabama, since March 2025. It was purchased in 2024 by a group that planned to turn it into a floating museum, but that effort failed. The vessel had crossed the Atlantic more than 800 times and carried prominent passengers including John F. Kennedy, Coco Chanel, Sean Connery, Marilyn Monroe, Salvador Dalí and Walt Disney. It also carried the Mona Lisa to the United States for exhibitions in 1963 and held the transatlantic speed record set on its maiden voyage in 1952.