Sunken treasure: Historic US ocean liner reborn as artificial reef

MIAMI: A majestic and all-but-indestructible 20th-century ocean liner that once ferried royal leaders, movie stars and even the "Mona Lisa" to the United States was being deliberately sunk on Wednesday to become the world's largest artificial reef.

Experts were conducting a controlled flooding of the 302-metre vessel, a veteran of more than 800 transatlantic crossings in the 1950s and 60s, which is set to reach its final resting place on the Gulf of Mexico's sandy floor, some 40km south-west of Destin-Fort Walton Beach, Florida.

"Two of the valves have been opened. The deployment process has started," said an official on the livestream operated by the city.

Florida's Okaloosa County, gambling that such a huge new reef would boost local tourism and attract diving and fishing enthusiasts, bought the long-decommissioned SS United States from a conservancy group for US$1 million in 2024.

The vessel — longer than the Titanic and the holder of the transatlantic speed record — will become the centrepiece of Okaloosa's undersea garden of sunken ships, including World War II vessels, tugboats and even a casino boat.

Captain Tim Mullane of Alabama-based maritime company Coleen Marine, which led the repurposing, has described it as "a great honour to put this fine vessel to rest... where it's going to serve a second life" promoting marine fauna, diving and fishing.

A year-long process of cleaning the vessel, removing all toxins such as fuel, paint and wiring, towing, environmental remediation, safety assurances and eventual sinking cost roughly US$13.5 million.

The SS United States, the result of a celebrated feat of mid-century American engineering, made its maiden voyage in 1952.

In its heyday, the luxury liner carried countless celebrities, including president John F. Kennedy, former King Edward VIII, Grace Kelly, Elizabeth Taylor and Salvador Dali. Future president Bill Clinton travelled on board on his way to study at Oxford.

Perhaps its most famous passenger was Leonardo da Vinci's "Mona Lisa", the 16th-century painting that visited America in 1963.

Within two decades of being built, the liner was out of service, falling victim to the growing popularity of air travel. It remained docked in Philadelphia for 29 years.

While the ship will rest at a depth of 180 feet, its top decks will be just about 55 feet below the water's surface, making them accessible to beginner divers.

Until now, the largest artificial reef was an aircraft carrier sunk 20 years ago off the coast of Pensacola, also in Florida.

Repurposing the SS United States keeps its heritage alive, said Okaloosa County tourism director Jennifer Adams Kemp.

"She's our country's flagship," she told CNN shortly before the sinking. "Why wouldn't we want to preserve that?"