They look like a slice of paradise that magically appeared right here in the Garden State, but they've proven deadly and dangerous, and you're being warned to stay away.

Countless — likely hundreds — abandoned quarries dot the Garden State. Boasting bright blue water unlike New Jersey's bays and creeks, locals find them extremely inviting during the summer months.

But if you take a dip, no lifeguard will be watching, and there's no telling what conditions and depths you may encounter.

"In a lot of these quarries, once you step off the bank, you can be 30 to 40 feet deep," said Downe Twp. Fire/Rescue and Dive Team Chief Clifford Higbee, Sr. "Once you have this quick drop-off, the water can go from 70-75 degrees to 45-50 degrees in the matter of one foot."

In that moment, he said, swimmers can cramp up or enter some form of shock, and there may be no place to go but down.

Higbee's team has handled recovery efforts on up to 10 quarry, or "blue hole," drownings over the past several years, he said.

Quarries are not currently tracked in New Jersey, but a 1990 report pointed to nearly 900 abandoned and active sand and gravel mining operations in the state.

Many are way off-road and not easily accessible by law enforcement and their vehicles. Even if gates and signs are nearby to keep swimmers away, "where there's a will, there's a way," Higbee said.

"You could find anywhere from a dozen to 50 people back at those blue holes on any given day," he said.

According to Lt. Kenneth Ryan with the Marine Services Bureau of the New Jersey State Police, their assistance may be requested by local agencies dealing with a quarry drowning.

"What we also provide to these townships and municipalities is sub-surface detection equipment ... in an attempt to locate that missing person for recovery," Ryan said.

He said the State Police recommends no swimming in any quarry on private or public land.

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