While doing English genealogy for a friend I happened upon some interesting maps. Look for erosion maps. For example look at East Riding of Yorkshire maps. You will see where over
30 towns that existed during Roman times are gone. They are now under the North Sea. They have disappeared since the 19th century. The sea has eroded/encroached into the Holderness
coast at least 1 1/2 to 2 miles or more. Now imagine what towns may have disappeared on the coast land of the British Isles and France etc. Does the land where your ancestors came from still exist?