From May, 2003 to September, 2006, staff from the RPM Nautical Foundation, the Mel Fisher Maritime Heritage Society, and the Florida Keys National Marine Sanctuary Submerged Resources Inventory team conducted magnetic surveys and underwater investigations of three areas of shoals and reefs surrounding the northern entrance to Turtle Harbor off North Key Largo, Florida. The purpose of this survey was to locate submerged cultural resources. Two sites, the wreck of the Spanish piratical slaver Guerrero and the grounding site of the HMS Nimble, both from 1827, were of particular interest. These surveys have located a large number of magnetic anomalies that result from shipwrecks or other cultural features.
The complex of reefs and shoals surrounding the entrance to Turtle Harbor is approximately 21miles south of the Port of Miami, 4 miles east of the northern portion of the island of Key Largo, and 3.5 miles north of the Carysfort Reef Lighthouse. This area is within the extreme northern reaches of both the Florida Keys National Marine Sanctuary and John Pennekamp Coral Reef State Park. The waters of Biscayne National Park are immediately to the north. Turtle Reef and Turtle Rocks form the eastern edge of this complex, and a series of unnamed reefs and shoals lie to the west and north.
The waters of the Florida Keys have long been considered a “ship trap,” and with their powerful combination of heavy ship traffic, miles of barely submerged reefs, and frequent hurricanes, thousands of ocean-going vessels have met their doom there over the last five centuries. Even under good conditions, mariners unfamiliar with the the Gulf Stream current and its vagaries near Florida reefs could meet with disaster. Writing in 1772, J.G.W. de Brahm observed:
“Many vessels, bound through to the New Bahama channel, were lost in fair weather: unacquainted with the stream’s eddy, and of soundings being under blue water, they were swept insensibly by the eddy to the westward; and when they found by their calculations that they had a good offing east of Cape Florida, stood north, and in lieu of entering the New Bahama Channel, run strait upon a reef.”1
Whatever the cause, many ships were wrecked, and some sank with no witnesses or survivors - they simply vanished into the sea after leaving their last port of call.
A considerable, if not the largest, portion of the modern historical research relating to the Turtle Harbor area are focused on the 1827 saga of the Guerrero and Nimble.2 This is the story of a Spanish piratical slaving brig carrying a cargo of 561 African people to sell to the Cuban plantations. The British Navy schooner HMS Nimble, was patrolling waters near the Bahamas for illegal slavers, and intercepted the Guerrero on December 19th, 1827. A chase began, and ended a few hours later near Carysfort Reef, when both ships struck bottom. The impact sank Guerrero in the shallows, drowning 41 of the captive Africans. Nimble was luckier; after many futile attempts, it was eventually floated free.
The story did not end there, though. Wreckers came to the aid of both ships, with two of them becoming the next victims of the piratical crew of Guerrero. After rescuing the crew and nearly 400 of the Africans, they were hijacked and forced to Cuba. Many of the pirates escaped, and most of their human cargo was sold. Those on the damaged Nimble could only watch. Eventually, Nimble did make its way to Key West with 121 of the Africans. After a long period of living as virtual slaves, those that survived were taken to Liberia to begin life anew.
Any search for these shipwreck sites should be guided by a number of specific physical signs. Not only was the Guerrero a complete loss, leaving an entire shipwreck on the bottom, but additional items relating to other ships were also lost or jettisoned in these events.
The primary tool used in these surveys has been the magnetometer. This is based on the assumption that man-made objects are distributed on the sea floor by intentional dumping, or accidental loss (i.e. dropped, snagged, or wrecked), and that many of these objects are iron. Variations and disturbances in the earth’s natural, ambient, magnetic field result from these ferrous objects, and the magnetometer is specifically designed to measure such anomalies.
Even wooden sailing ships used iron in a variety of ways - to fasten the hull, as components of the rigging, in ground tackle and artillery, as ballast, cargo, and tools among many other items. When ships are sunk, these iron components create magnetic disturbances at the position where they lie, and these are easily detectable through the use of a magnetometer. Though a magnetometer will not find all the various portions of a shipwreck, it can find a significant, representative cross-section. As iron objects were distributed throughout the vessels, they also are distributed across the ship’s wreck site, providing an adequate sample for determining its location. Historical research has made it clear that ships were lost in the Turtle Harbor area, and their remains should still be there.
The reefs and shoals surrounding the northern entrance to Turtle Harbor, bounded roughly by the 20-foot contour line, were chosen for examination. The areas within these shallower portions of the reef were considered the most likely places for ships to have grounded and wrecked, and to harbor the desired targets. As a result of these surveys, over 80 targets have been located, including a number of shipwrecks. Research at these sites continues.
1 J.G.W. DeBrahm The Atlantic Pilot, 1772. Reprinted by University of Florida Press, Gainesville, 1974.
2 Aside from this effort, Florida Keys Historians Gail Swanson, Jim Clupper, and Denis Trelewicz have all made significant efforts to uncover the details of this tragic, complicated and fascinating story. Swanson has recently published a book, The Slave Ship Guerrero, (Infinity Press, 2006), which nicely summarizes the saga from the time of the ships’ sinking, to what became of the African survivors’ lives in Liberia.