The last time I spoke with Greg Brooks, the Westbrook man who sold his swimming pool business nearly 20 years ago to search for treasure-laden shipwrecks in the Caribbean, he believed he had located one of the richest vessels ever lost at sea.

That was in July, and he preferred not to reveal the name of the ship until he had staked his claim in a Florida federal court. But he did say, with undisguised enthusiasm, that the vessel could yield a treasure that would dwarf the $400 million bounty that famed salvager Mel Fisher raised to international fanfare from the wreck of the Nuestra Senora de Atocha in the 1970s.

According to a maritime law report published recently in Florida’s online Daily Business Review, Brooks got his federal claim in October, which allows his Portland-based Sub Sea Research Inc. to “arrest” the shipwreck and protect it from modern-day pirates. If Brooks’ extensive research proves accurate and the ship turns out to the 18th century wreck called the Notre Dame de Deliverance, he said, it could contain a kingly hoard of Spanish gold, silver and jewels worth upwards of $3 billion.

“You could say I’m having a hard time sleeping these days,” said Brooks, who was out shopping in Portland when I caught up with him by phone on Friday. “At this point, we can’t be 100 percent certain that it’s the Deliverance. But with all the evidence we have so far, we’re 99 percent positive this is the one.”

Maritime records indicate that the Notre Dame de Deliverance was a 166-foot, armed merchant vessel that was owned by the French West Indies Co. and sailed under a Spanish flag. The ship is believed to have sunk in a hurricane on Nov. 1, 1755, a day after departing from Havana, Cuba, for Cadiz, Spain. Records show that it was carrying 512 passengers and crew when it went down.

An incomplete manifest of the Deliverance’s cargo, which was owned by Spain’s King Charles III, indicates that the sunken treasure includes 17 chests filled with nearly 1,200 pounds of gold bullion, 15,000 gold doubloons, six chests of gems and more than a million silver pieces. The manifest does not take into account any valuables that might have belonged to the passengers.

The Atocha, on the other hand, has yielded 115 gold bars, 900 silver bars, 200 pounds of gold, 3,000 emeralds, 135,000 silver coins and fewer than 100 gold coins.

The Deliverance site is located in 200 feet of water about 40 miles off Key West, Fla. The company’s research to date includes surveys of the site by dive teams and state-of-the-art remote sensing devices, an exhaustive examination of historical records, and the discovery that some silver items – a crucifix, plate and some coins among them – were brought up by other salvagers years ago. On Thursday, Brooks said, he learned that a shrimp fisherman brought up in his net some 30 to 40 silver ingots, worth $800,000, but threw them back because he thought they were worthless “big, black blobs of metal.”

Brooks said he is awaiting the permit that would allow his 12-member crew soon to begin a detailed inventory and camera survey of the wreck site. By spring, he said, he hopes to have the permit necessary to salvage the entire site.

“We could start working at the site within a couple of weeks,” said Brooks, whose team now includes the former chief archaeologist and two attorneys of the late Mel Fisher. “The weather has been blowing every day down there, but as soon as it clears my guys are ready to put down the cameras.”

But such an operation is much more complicated, of course, than simply hauling up suspected riches from the ocean floor. The wreck lies “substantially” within the Florida Keys National Marine Sanctuary, but outside Florida territorial waters. According to the Daily Business Review story, the law considers wreck sites “submerged cultural resources.” Those in the sanctuary – a federal trusteeship co-administered by the U.S. National Oceanic and Atmospheric Administration and the state of Florida – are strictly regulated. Sanctuary rules, stemming from Mel Fisher’s legal battle with Florida over the Atocha treasure, allow private salvagers to work wrecks on public property as long as a site’s historic value is preserved. Which means, said Brooks, that salvagers can get title to such valuables as bullion, coins and gems that are considered by archaeologists to have no real historic interest. Unique artifacts, however, remain public property.

Brooks said that because Florida has no claim on the site, and already has 23 million artifacts from other wrecks that have yet to be cataloged, he would like to share the Deliverance’s potential historical treasures with the people back home in Maine.

“You can have items of high historic value as long as you have a public museum to house them and where people can come and see them,” Brooks said. “And that’s what we’re working on right now, a feasibility study to make a world-class museum and aquarium that would require no public funds. We’d build it with our own money.”

Brooks said he has spoken about the plan with Gov. Angus King and is hoping to get support from Sen. Susan Collins as well.

“We need for the people of Maine to say that they want something like this,” said Brooks, who doesn’t rule out the possibility that Florida would dispute the ownership of certain items recovered from the site. “I really want this to happen here in Maine. This dream has been a long time coming, but I think we’re there.”