Divers are in the waters of Biscayne National Park and trying to solve a mystery almost two centuries old.
The underwater archaeologists with the National Park Service are out to make rare find. They are on a hunt for a ship called the Guerrero that was carrying slaves to the Americas.
"The possibility of finding a ship like the Guerrero is highly significant," said Dr. Fritz Hanselmann with the University of Miami Rosenstiel School of Marine and Atmospheric Science.
"There have only been two identified slave ship wrecks in the archeological record to date which makes the Guerrero of extreme importance."
On the day we went into the water with Hanselmann and National Park Service archeologist Joshua Marano, they were diving in a location about 15 miles southeast of Homestead.
Marano had his writing tablet clutched in his arms when he heads underwater. He doesn't want to miss documenting the slightest detail. After all, he's looking for something no one has been able to find for 200 years.
"It's a significant story in South Florida that hasn't really been told," Marano said. "It was a pirate slave ship that was carrying 561 enslaved Africans across from Africa in 1827."
Here's the history of what happened, according to the Park Service. It's a story that's been made into a documentary funded by the National Park Service.
In the 1820's, slavery was still legal in the US. Pirates took over the slave trade across the Atlantic because both the US and Great Britain had outlawed transporting them.
A British warship named the Nimble was out on a mission to stop pirates and the crew spotted the Guerrero off the South Florida coastline and started to attack.
A naval gun battle ensued and while trying to escape the Nimble, the Guerrero ran aground and eventually sank. The British ship did too. The Nimble's logs were used to provide some information, but no one has been able to determine exactly where the ships went under.
"If you read the log of the Nimble, which has been preserved, it says it gave chase to a suspicious looking brig sighted off of its bow," Marano said. "They ended up chasing each other and had a running gun battle with one another until they didn't exactly know where they were."
Of those enslaved on the Guerrero when it sank, 41 died. The pirates manning the ship hijacked two other ships that had come to help the Guerrero. The pirates took the 500 remaining slaves to Cuba. Some, Marano says, ultimately were sent to Florida.
The National Park Service divers and the other researchers started out with about a thousand linear miles to search.
They've done about half of that and now they have about 500 what they call 'anomalies' to take a closer look at to see if it leads them to the Guerrero.
They use an underwater metal detector pulled behind a boat that alerts them where to look. They'll sometimes use a device that looks like a large blow dryer to clear the sand on the ocean floor.
NBC 6 Photojournalist John Lang captured video of the divers scanning the bottom when they came across what may have been a rib making up the hull of a vessel.
These locations are marked and items are placed in plastic bags to bring on land to investigate.
"One of the sites that we've found was an actual dump of cannon balls and other heavy objects," Marano said. "We've recovered some of those objects and conserve them to hopefully see if there was any kind of mark or marking or anything like that may tell us whether or not this came from a British warship."
The search is made more difficult with the passage of time and nature's impact on what's on the ocean's floor.
"The problem is as ship wrecks sit underwater they tend to work to become one with their environment and reach equilibrium. And so corals grow over them, they kind of degrade," Marano told us. "They become very difficult to differentiate and identify individual features."
While items may look the same to the untrained eye, the quest to know more motivates these researchers. "The ones that we are looking for provide us with a physical connection to our past and allow us to actually interact with those who preceded us and learn more about them," Hanselmann said.
The hope is the searches can produce results like some of the well documented wrecks in the National Park not far away that have been preserved.
For Marano and the other researchers, there's a lot of work to do. "The Gulf Stream just off shore of the Florida Keys, I always like to refer to it as the maritime equivalent of I-95 or maybe the Turnpike." Marano said. "Everything that ever traveled through the Florida Keys, particularly during the age of sail, had to pass ridiculously close to the Florida Keys."
And he says that would include the still missing Guerrero.