Faint signal leads treasure hunters to massive discovery at legendary 400-year-old wreck

A treasure-hunting crew searching a legendary 17th-century underwater shipwreck off the Florida Keys has recovered a massive 55-pound copper ingot — the latest find along a trail that its captain believes could lead to more treasure.

The ingot was found by divers with Mel Fisher's Shipwreck Expeditions at the wreck site of the Nuestra Señora de Atocha, about 35 miles west of Key West.

The Spanish treasure galleon was on its return voyage to Spain when it sank in a hurricane off the Florida Keys in 1622 — carrying silver, gold and emeralds.

MYSTERY OF GOLD COIN SHIPWRECK FINALLY UNMASKED AFTER 30 YEARS: 'FANTASTIC CONCLUSION' Mel Fisher began searching for the Atocha in 1969.

He spent years recovering artifacts from the wreck before his company prevailed in a lengthy legal battle over rights to its treasure in 1982.

Fisher's team discovered the Atocha's famed "Mother Lode," or main cargo deposit, in 1985 — and the site still yields new finds decades later.

Photos show the 55-pound copper ingot — or copper bar — heavily coated in marine encrustation after spending over four centuries underwater.

In an August press release, Mel Fisher's Shipwreck Expeditions said the ingot has an estimated value of about $18,000 to $25,000.

UNDERWATER ROBOTICS EXPERT REVEALS 'SHIPWRECK CITY' HIDING BENEATH MAJOR URBAN LAKE Captain Drake Nicholas was retracing an area from the salvage vessel DARE when his metal detector picked up a faint signal, he told Fox News Digital.

The captain said he was following a "tight trail of coins" at the time.

"Faint hits are always the most exciting because they lead to, you know, stuff very deep in the mud," said Nicholas.

"And I got that very faint hit.

I dug down like I always do ... and it got louder, and that's, you know, when the excitement really kicks in." DIVERS UNCOVER HUNDREDS OF ANCIENT RELICS NEAR SHIPWRECK UNTOUCHED FOR 2,100 YEARS Nicholas said he initially mistook the ingot for a cannon due to its rounded shape, large size and bronze-copper coloring.

"I was so excited," he said.