This offshore shipwreck site lies in the shallow coastal waters near Mafia Island, a relatively remote island off the southern coast of Tanzania in the Indian Ocean. The site is submerged and accessible only by boat, with no above-water features visible to casual observers — making it a destination almost exclusively for divers and researchers. Local fishermen have long been aware of the coordinates, and their knowledge reportedly led Gates and marine archaeologist Bridget Buxton to the location during filming. Underwater, the site is believed to preserve a scatter of ceramic vessels alongside ballast stones — the kind of assemblage that often survives long after a wooden hull has decayed entirely. The pottery recovered has been assessed as post-medieval in date, suggesting the wreck may represent one chapter in the long maritime trade history that made this stretch of the East African coast significant for centuries. Gates investigated the site as part of a broader search for Rhapta, the so-called "Atlantis of Africa," a lost ancient trading emporium believed by some researchers to lie somewhere in this region.
Rhapta mentioned in the Periplus of the Erythraean Sea as a major East African trading hub — the broader regional context Gates was investigating
The shipwreck at the offshore site is believed to date to the post-medieval era, based on ceramic assessment, though the vessel's origin and identity remain unconfirmed
Josh Gates and Bridget Buxton dive the site during filming of Expedition Unknown S13E05 "Chasing Africa's Atlantis"
The episode brought Gates together with archaeologist Caesar Bita and Dr. Felix Chami, whom Gates introduced on camera as "the world's foremost authority on Rhapta" — a characterization Chami accepted. Dr. Chami has argued that Rhapta lies in the Mafia Island region, and the broader investigation in S13E05 centered on evaluating his claims alongside physical evidence gathered in the field, including the offshore dive.
From a mainstream archaeological standpoint, shipwreck sites in shallow coastal waters near historic ports are regarded as valuable but fragmentary evidence of trade activity. Ballast stone assemblages are particularly significant because they can survive for centuries after organic hull material has vanished, and ceramic cargo — when identifiable — can sometimes indicate a ship's port of origin and approximate period. That said, a post-medieval ceramic date places this wreck well after the era of Rhapta, which ancient sources suggest flourished roughly two thousand years ago, so any direct connection between the two remains speculative at best.
The genuinely contested question hanging over this site — and over the broader Mafia Island investigation — is whether the underwater and coastal formations in the area are the result of human construction or natural geological processes. Gates himself drew the comparison to the Yonaguni formations in Japan, another site where that debate has never been fully resolved. The ceramic and ballast evidence from the offshore dive adds an intriguing data point, but as Gates' own framing made clear, it is far from conclusive proof of anything.
What the episode contributed was a rare on-camera dive of a site known mainly to local fishermen, and the recovery of physical material — ceramics and ballast stones — that researchers can potentially study further. The episode does not claim to have identified the wreck's vessel or confirmed any link to Rhapta. It presents the find honestly as one piece of an incomplete puzzle in a region that, as Gates observed, may once have been "a bustling emporium where the treasures of the continent were traded with the Roman Empire."
Mafia Island lies within the Mafia Island Marine Park, one of East Africa's protected marine areas, making its surrounding waters home to diverse coral reef ecosystems.
The ancient trading port of Rhapta is described in the Periplus of the Erythraean Sea, a Greek-language merchant's guide believed to date to roughly the 1st century AD — making it one of the earliest written references to the East African coast.
Ballast stones from shipwrecks are among the most durable archaeological artifacts in maritime contexts because, unlike wood or cloth, stone requires no organic preservation conditions to survive on the seafloor for centuries.
Local fishermen on Mafia Island reportedly maintained knowledge of the offshore coordinates that led Gates and Bridget Buxton to the dive site — an example of how traditional ecological and navigational knowledge often predates formal archaeological survey.
The offshore shipwreck site has no formal visitor infrastructure and is accessible only by boat from Mafia Island — generally a remote destination with limited tourist facilities. Diving in these waters is possible but visitors should arrange certified local dive operators and check current maritime and safety advisories before planning any underwater excursion.
Dar es Salaam, Tanzania — approximately 160 kilometers north of Mafia Island, with small aircraft and occasional ferry connections to the island.
The East African coast around Mafia Island is generally most accessible during the dry season, roughly June through October, when seas tend to be calmer and diving conditions more favorable. The long rainy season from March through May can make offshore travel significantly more difficult.
Indian Ocean
The Indian Ocean formed the broader maritime trade network within which Mafia Island and the search for Rhapta are situated, and Gates has investigated multiple sites connected to ancient Indian Ocean commerce.
Dwarka
Dwarka is another submerged ancient city that Gates has investigated — like Rhapta, it sits at the intersection of underwater archaeology and hotly debated questions about whether ancient settlements lie beneath coastal waters.
Kingdom of Kush Pyramid Tombs
The Kingdom of Kush represents another chapter of sub-Saharan African civilizational history that Gates has explored, providing regional and thematic context for the search for Rhapta as a sophisticated lost African trading center.