As vast quantities of seawater was locked in thick ice sheets and glaciers, which periodically advanced and retreated, the sea level was up to 130 metres lower than it is today, but with many local variations of where the sea shore was at any given time.
Early humans colonised and re-colonised what we now know as Europe, moving across lands that are now covered by the sea. These migrations occurred according to changes in factors such as the availability of food and other resources and the climate.
Around 20,000 years ago, rising sea levels caused by the melting of the ice caps and glaciers began to disconnect Britain from continental Europe, although the Channel and the North Sea did not reach their present extent until around 7000 years ago.
Evidence of landscapes which are presently submerged has been discovered since the 19th century. Modern techniques from marine archaeology to other scientific disciplines such as marine geology enable previous work to be analysed and presented.
Changes in the coastline and the sea level have been occurring for thousands of years. Today on land, evidence of the lives of early peoples can be seen in terrestrial prehistoric landscapes.
Although the inundation by the sea of large areas of land can date to as recently as the medieval period, as on the Isles of Scilly, far more extensive changes occurred in prehistory.
The British Palaeolithic and Mesolithic are marked by significant changes in climate, sea level and geomorphology which affected the pattern of human occupation throughout prehistory. Different climatic conditions can be identified and archaeologists are particularly interested in the warmer inter-glacial periods when people may have been present.
Across the coast and into the sea geomorphological features from these periods like palaeo channels, gravel banks and river drainage systems, can be seen. These and other features can be indicated by outcrops of peat and the remains of prehistoric forests on the seabed.
Although archaeological sites remain hard to recognise under water, there have been some notable finds, such as the collection of Middle Palaeolithic hand axes from Area 240 in the North Sea, and the evidence of Mesolithic occupation at Bouldnor Cliff in the Solent.
Historic England's work on submerged landscapes, as described below, is primarily aimed at identifying and mapping those areas with a high potential for similar finds to occur.
From this point too, over time human kind developed many ways to exploit the seas and other waterways for purposes such as travel, communication and trade, all of which can be informed by the study of wrecks.
Coastal survey provides the opportunity for gaining new information from the coastal edge and inter-tidal areas.
For the seabed Historic Seascape Characterisation techniques are important for setting the context for the understanding of the potential for past occupation of lands now submerged.
The archaeological surveys carried out in advance of development on the seabed under the marine planning system also contribute to our knowledge.
With the growth in seabed development, such as the offshore renewables sector, important information can be gained from surveys carried out for marine planning purposes when these developments are authorised.
New knowledge can also come from both chance discoveries and voluntary archaeological activities by divers and, on Protected Historic Wreck Sites, through continued work of Licensees.
Investigating the Submerged Pleistocene Landscapes of the Wallet, off Clacton
Historic England commissioned specialists from the University of Southampton to produce a report on Submerged Pleistocene Landscapes of the Wallet, off Clacton.
Previous work highlighted three key areas of research that were needed: large scale offshore characterisation projects, research on Pleistocene deposits at a smaller, targeted level, and establishing best practice in the investigation of these deposits. This project used information derived from trawled animal bones to target specific, high potential areas of seabed for investigation. As such it addressed the latter two areas of identified gaps in research and aimed to provide a new method for the identification and investigation of fragmentary Pleistocene submerged deposits.