A ship last used by the U.S. Air Force to track missiles and spacecraft became the world's second-largest intentionally sunk artificial reef Wednesday.

Using explosives attached to the hull, crews sank the decommissioned Gen. Hoyt S. Vandenberg about seven miles off Key West, Fla.

The scheduled 10 a.m. blast to force the hulking vessel to the ocean floor was delayed by about 20 minutes because of sealife in the vicinity — specifically, sea turtles.

Officials hope the newly sunken ship will attract fish and divers and relieve recreational pressure on nearby natural reefs.

Explosives attached to the vessel's hull were detonated to flood the 17,000-ton, 523-foot-long vessel that was first built as a cargo ship in World War II.

It was expected to settle on the sandy bottom in 140 feet of clear water only minutes after it was sunk.

The project has been years in the making. The cost is about $8.6 million, from acquiring the ship to cleaning it.

Officials in the Florida Keys expect it to pay dividends, up to $8 million in annual tourism-related revenue, mostly from divers flocking to get a look at the underwater spectacle and related businesses.

The idea is to not only to attract tourists, but to help protect the Keys' natural reefs, already suffering from excessive diving, snorkeling and fishing along with warming ocean temperatures.

Joe Weatherby, project organizer at an artificial reef company called Reefmakers, said people — and fish — will now be drawn to the wreck from nearby natural coral, "giving the reef a breather, which is what it needs."

Preparation for sinking has taken months of inspections and cleanup to remove contaminants. Workers hauled off more than a million feet of wire, 1,500 vent gaskets, dozens of watertight steel doors, 81 bags of asbestos, 193 tons of potentially cancer-causing substances, 46 tons of garbage that could come loose and float to the surface, 300 pounds of materials containing mercury and 185 55-gallon drums of paint chips.

The cleanup was performed at two Norfolk, Va., shipyards before the boat made the 1,100-mile voyage, arriving in Key West on April 22. Permitting was required from 18 local, state and federal agencies.

The Vandenberg began as the Gen. Harry Taylor and was later commissioned by the Army as a transport vessel, ferrying troops and supplies from San Francisco to island bases in the western Pacific Ocean in 1944.

In 1945, it carried troops home from Europe near the end of World War II. It was later used by the Navy as a transport ship, and was transferred to the Air Force in 1961, when it was renamed the Vandenberg.

For about 20 more years, the ship served as a missile tracker throughout the height of the Cold War and was retired in 1983.

Mac Monroe, a former mission controller aboard the Vandenberg, said he was pleased the ship won't be turned into scrap metal.

"It's nice to see the old rust bucket again," Monroe said on a recent trip to Key West to see the ship. "And it's a positive outcome for it be sunk and become something useful again."

Organizers say it will serve as "the anchor" to the region's wide array of existing sunken vessels and wrecks from Key Largo to Key West, where some estimate there's a shipwreck about every 300 yards.

The rusty hulk is now tied up at a dock awaiting its final resting place on the ocean floor.

The Vandenberg sinking apparently went more smoothly than that of the Spiegel Grove off Key Largo in 2002.

That 510-foot decommissioned landing ship dock partially sank upside-down, hours before an attempt to scuttle it to create an artificial reef.

The sudden sinking sent 40 workers onboard scrambling for safety and left the ship's bow sticking out of the water for three weeks.

The first-largest intentionally sunk artificial reef is the USS Oriskany, which was sent to the bottom of the ocean three years ago off the coast of Pensacola Beach in the Florida Panhandle.