Professor Lucy Blue speaks with Otto Uldum, Maritime Archaeologist and curator at the Viking Ship Museum in Roskilde, Denmark about the remarkable discovery of a medieval cog found in 2021 in 14 metres of water in the Øresund Strait near Copenhagen. Dendrochronological analysis of the sapwood date the vessel to the early fifteenth century and confirmed that it was built in the Netherlands, while some of the planking timber originated from Pomerania in present-day Poland, revealing the far-reaching timber trade networks of the period.

The ship displays distinctive cog shipbuilding techniques, including scarf joints, clinker planking, clench nailing, and square-section iron nails, all of which created a hull that was both light and exceptionally strong. Unlike many other vessels, cogs were characterised by a broad flat-bottomed midship section that enabled them to carry cargoes of up to 300 tons. Named Svælget 2, the vessel measures 28 metres in length and is among the largest and best-preserved medieval cog ever discovered. Every surviving timber has now been raised and laser-scanned, and once conservation is complete the ship will be reassembled alongside its extensive rigging assemblage, including a rare complete set of deadeyes with surviving rope fragments. Many questions, however, remain unanswered. The nature of its cargo is still unknown, and the circumstances of its loss remain elusive. Could Svælget 2 represent the last gasp of cog usage within the trading networks of the Hanseatic League?

Professor Lucy Blue takes us to China to discuss the recovery and investigation of the Yangtze River Estuary No. 2 shipwreck, discovered in 2015 by the Shanghai Museum archaeologists with the help of the local fisherman. Dr Xiaolin Ma and Dr Prof. Zhanghua Wang from East China Normal University, Shanghai talk about their roles in understanding the life history of the ship. Buried for over 150 years beneath fine sediment in around 10 metres of water at the mouth of the Yangtze River, this 38-metre vessel is the largest and best-preserved ancient wooden shipwreck discovered in China. The wreck was lifted inside a container (48 meters long, 19 meters wide, and 9 meters tall) with surrounding sediments and is now being carefully excavated in Shanghai’s disused shipyard. Scientific analysis has revealed remarkable details of its cargo and is on going. Using methods, including sedimentary environmental DNA (eDNA) analysis that identifies the genetic material of all organisms from sediments sealed inside the pottery jars, researchers were able to reveal insights into the nature and origin of elements of the cargo no longer visible in the archaeological record. Excavation continues in Shanghai, as plans are underway to create a museum to house the Qing Dynasty ship and its finds.

The project would like to acknowledge Mr Yang Zhai from Shanghai Cultural Heritage Conservation and Research Centre, who provided chances for studying the sedimentary DNA of a shipwreck; Dr Shaoqing Wen from Fudan University, who provided ultra-clean laboratory and equipment for eDNA analysis and helped with the analysis. They also would like to thank Haixia Wen and Xin Wei from East China Normal University and Zhihang Ma from Fudan University who measured the environmental parameters and performed data processing.