Investigations of ship timbers, cargo bricks, and clay pipes recovered during underwater excavations confirmed the identities of the wrecks, which historical sources report were lost in 1710. For the first time, museum experts have documented that the two shipwrecks are named Danish slave ships from the 18th century.

The confirmation follows scientific analyses from a 2023 underwater excavation when marine archaeologists from the Viking Ship Museum collected wood samples from one of the wrecks along with cargo bricks and several clay pipes.

“The analyses are very convincing, and we no longer have any doubts that these are the wrecks of the two Danish slave ships,” said David Gregory, marine archaeologist and research professor at the National Museum of Denmark, where he heads the new Maritime Research Centre Njord. “The bricks are Danish, and so are the timbers, which are charred and sooty from a fire. This fits perfectly with historical accounts stating that one of the ships burned.”

Gregory led the excavation alongside Andreas Kallmeyer Bloch, a marine archaeologist who has spent years investigating the origins of the ships.

“It’s been a long process, and I’ve come close to giving up along the way, but this is undoubtedly the craziest archaeological excavation I’ve ever been part of,” Bloch said. “Not only because it matters greatly to the local population, but also because it’s one of the most dramatic shipwrecks in the history of Denmark. Now we know exactly where it happened. This provides two pieces that have been missing from Danish history.”

Samples from the excavation were analyzed at both the National Museum and the University of Southern Denmark, confirming the historical record. Dendrochronological (tree-ring) analyses of oak wood from one of the wrecks determined that the timber originated from the western Baltic Sea region, which includes northeastern Germany’s Mecklenburg, Schleswig-Holstein, Denmark, and Scania, and was cut down sometime between 1690 and 1695. The wood’s charred condition matches historical accounts of a fire aboard one of the ships.

Additionally, Dutch-produced clay pipes found at the site, common on Danish ships, were dated to just before the wrecks occurred. Experts noted that clay pipes typically were not used for more than five years, supporting the dating of the shipwrecks to 1710.

Historical records state that Fridericus Quartus was set ablaze, while Christianus Quintus broke free after its anchor rope was cut, causing the ship to run aground in the surf. Until now, the precise locations of the wrecks had remained unclear.

While it had long been known that two shipwrecks lay in the shallow waters off Cahuita Beach, they were often assumed to be pirate vessels. However, in 2015, American marine archaeologists discovered yellow bricks in one of the wrecks, raising new questions. The yellow bricks matched those produced in Flensburg for use in Denmark and its colonies, in contrast to the materials preferred elsewhere in Europe at the time.

The investigations have been conducted in collaboration with the National Museums of Costa Rica and Denmark, the Viking Ship Museum in Roskilde, the University of Southern Denmark, the Archaeological Commission of Costa Rica, and other organizations.

Recently, a series of tombs containing indigenous skeletons and artifacts from the pre-Columbian era were discovered in Cartago Province.

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