During the 1980s Ron Hall, a local boat owner and archaelogist, noticed a number of wooden structures within the intertidal zone of the Blackwater Estuary, Essex, UK.
These structures consisted of lines of wooden stakes extending out into the subtidal and were only rarely exposed, during low tides.The structures were identified as wooden fish traps and dated to within the seventh to 10th century AD.
Aerial photography sponsored by Essex County Council established the presence of a large number of fish traps which have been drowned by post-glacial rising sea levels. The isolated and often dangerous location of the traps prevented accurate mapping and so the size of this significant archaeological resource was undetermined. In 1998 the Royal Commission on the Historical Monuments of England commissioned a geophysical survey by the High Resolution Marine Seismology Group of Southampton University.