"These reefs provide quality habitat for marine life off our coast which benefits not only the environment but also local businesses," said Ocean City Mayor Rick Meehan.

The 18-ton stainless steel cars -- minus wheels, windows and doors -- were stacked two-high on a barge where a bucket crane with a specially designed hydraulic lift picked them up one by one and dropped them into 90 feet (30 metres) of water.

As journalists watched from five smaller boats, the cars landed on their sides with a bang, and blew whale-like jets of spray as air escaped from their interiors. They disappeared a few seconds later beneath the gray-green waters.

The cars, dating from 1964, were among 1,662 that have been retired by New York's Metropolitan Transportation Authority and will be used by a number of states on the US East Coast to create the reefs to buoy local fishing industries.

Maryland plans four more subway-car reefs and since 2001 others have been created in Delaware and New Jersey waters from an earlier batch of about 1,200 cars released by the MTA.

Jeff Tinsman, Delaware's reef program coordinator, said a 600-car reef in that state's waters had increased the local fish population by 400 times, and boosted the number of angling trips to 13,000 a year from 300 before the reef was created.

PREDATOR PROTECTION

The reefs attract fish because they provide protection from predators, and generate food like mussels, shrimp and crabs that quickly colonize the structure. About 95 percent of the seabed off the US mid-Atlantic coast is naturally bare sand, which is much less likely to attract fish, Tinsman said.

Officials hope the new Maryland reef will become home to such inshore species as black sea bass, tautog and summer flounder. These in turn should attract game like marlin, tuna and dolphin and the recreational fishermen, who contribute about $1 billion a year to Maryland's economy.

Martin Gary, a fisheries biologist with the Maryland Department of Natural Resources, said some of the targeted species have been depleted by overfishing. He promised that officials will take steps to prevent that from happening again around the new reef by imposing rules on the size and number of fish that can be caught, and the seasons when they can be taken.

Gary said the new reef, at a favourite local fishing ground called Jackspot, is deeper and farther from the shore than other subway-car reefs, and will hopefully attract inshore fish and the deep-water migratory species that feed on them.

Any environmentally hazardous materials including PCBs and petroleum lubricants were removed from the cars by the MTA at a cost of $8,000 per car to comply with federal government regulations.

The nonprofit Ocean City Reef Foundation paid $600 per car to transport them 30-hours from New York City to create the reef.

In their final resting place -- where they are expected to last 40 years or so -- the subway cars begin another useful life, Gary said. "It's hard to believe they were in service as little as 10 days ago."