San Pedro de Alcantara

    A 1786 shipwreck shocked the financial markets of Spain. Eventually, the precious cargo was salvaged and the scattered remains are now being investigated.

The American metal trade

During the 16th, 17th and 18th centuries, Portugal and Spain imported enormous quantities of precious metals from Central and South America. So much that it probably caused a world-wide inflation.

San Pedro

porcelain in concretion

Piece of porcelain found encrusted to an iron object.

San Pedro de Alcantara was a 64 gun Spanish man-of-war, built in Cuba in 1770. In 1784 she loaded copper, silver and gold from Peruvian mines. She also carried a collection of ancient ceramics of the Chimu culture, as well as captured prisoners from the Tupac Amaru independence movement. Many years later, a modern guerrilla would carry the same name.

Unfortunately the ship was heavily overloaded. She carried about 600 tons of copper, 153 tons of silver and 4 tons of gold. The silver was minted to coins, mostly 8 reales pieces, "pieces of eight". The cargo was about twice as much as usual for such a ship. The captain was even warned that the ship would risk losing its bottom in a storm. However, there were no exact rules for overload in those days, so she sailed away.

Why was this ship so heavily overloaded, risking the valuable cargo? One reason is that the independence war with England against the newly-founded USA together with France and Spain ended in 1783. The English blockade against South American ports was lifted and there were large quantities of goods waiting to be shipped. The Spanish authorities were also in a hurry because of the recent native Tupac Amaru rebellion.

Rocks near the wreck site

Violent rocks near the wreck site. The cable to the dive site is in the foreground.

During her voyage from Peru, San Pedro de Alcantara was constantly leaking, and the crew had a hard time manning the pumps. After rounding Cape Horn, the ship was taken in for repair at Rio de Janeiro. When the leaks had been tightened, the ship continued in early 1786.

In a dark February night, she hit a rock near Peniche in Portugal, 90 km north of Lisbon. The wind was fair and there is no clear reason for this accident. Perhaps the heavy overload made the ship difficult to navigate. The ship had a speed of 6 knots, and the impact was so hard that the lower part of the hull broke off around the waterline and sank immediately. The upper part of the hull with deck and rigging just continued forward and floated for some time. 128 people drowned and about 270 survivors made it up on the rocky coast.

diving operations of 1786

Free divers salvaging the cargo in 1786.

The copper, silver, and gold lost in San Pedro’s cargo corresponded to about 1/12 of the total currency circulating in Spain. The Spanish king was alarmed and immediately sent his representative to the site. An enormous diving enterprise was initiated and divers were hired from all around. During the following three years more than 40 divers worked full-time, and almost all of the cargo was salvaged. This was considered a great success, since the cargo was worth much more than the ship. The diving operation was by then the largest ever in European history.


During the next 200 years, the oral tradition of San Pedro lived on among the inhabitants of Peniche. The event was also well remembered in the Spanish archives. The Archivo de las Indias in Seville has about 40,000 pages covering this event.

securing an artefact to be lifted

During the summers of 1987-99 archaeologists Jean-Yves Blot and Maria Luisa Pinheiro-Blot, working for the Portuguese Institute of Archaeology, have investigated the wrecksite in collaboration with many colleagues and volunteers, many of whom became friends for life after years in a row spent together under the sun or in the sea. Thousands of artefacts have been found underwater, but the only wooden fragments found were imbedded in the side of a protruding rock, possibly the actual impact point. The rest of the hull was either salvaged in the 18th century or smashed to pieces in the shallow turbulent water, and consumed by the shipworm Teredo Navalis.

The sea bottom consists of irregular rocks, where cavities and cracks are filled with stone and sand. Almost all finds consist of small objects, spread over a large area, and located in such cavities. Any object laying openly on this sea bottom would have been destroyed or washed away by the violent sea. It is also difficult to distinguish San Pedro artefacts from the remains of the steamer João Diogo, which sank on the same spot in 1963.

author going to the siteAmong the most common finds are fragments of pottery, encrusted iron objects and pieces of lead sheathing. Only one of the cargo’s copper bars has been found. The largest object is a swivel gun from the forecastle. Inside one of the large concretions recovered, an intact wooden block has been found.

The site is difficult to reach from the high rocks at the coast. In order for the divers to reach the site, a cable lift has been created, transporting divers and equipment.

The seemingly chaotic dispersion of artefacts poses an interesting question. How are loose objects dispersed from a shallow shipwreck? Nobody knows, but important factors seem to be the direction of the swell, currents, and the bottom topography. There have been efforts to explain this using mathematical models, as suggested by the late archaeologist Keith Muckelroy, but a working model remains to be constructed. Meanwhile, the three-dimensional positions of recorded artefacts are being skeleton in chains, presumably Inka prisonerentered in the Web software, developed by Nick Rule. A statistical analysis is also being made between the weights of artefacts and their distances to the ship’s point of impact. It is like trying to reconstruct a plane crash only from fragments.

In chains forever

Parallel with the underwater fieldwork, the graves of some of the victims from San Pedro have been located. Osteological analysis revealed that most skeletons were of European origin and some were native South American. The European dead had been placed neatly in individual graves. The Peruvian prisoners, however, had been thrown in a pile, some with chains still around their feet. Not even in death were they considered equals. Continued=>

by Per Åkesson, Aug 1999

Related texts

Related link

  • Our daily diary was published on


AIMA Bulletin 22: 1998

Archaeological Computing Newsletter 51: 1998

Al-Madan, Portugal, no 7: 1998

Mundo cientifico, Spain, no 113, 1991

J-Y Blot & ML Pinheiro Blot: O "interface" história-arqueologia: O caso do "San Pedro de Alcantara" 1786 (Academia de Marinha, Lisbon 1992)

Jean-Yves Blot: Underwater Archaeology (Thames & Hudson/Abrams 1996)

Contemporary painting by Jeal Pillement

Contemporary engraving by Luis Paret

Photos by Maria Luisa Pinheiro-Blot, Fernando Moreira dos Santos and Jean-Yves Blot. Engraving by Luis Paret. Page rev apr '10

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