Lindsey was between the River Humber on the north and the Witham on the south. To the east lay the North Sea and the west border was the River Trent. The Roman canal called Foss Dyke connected the Witham with the Trent on the southwestern border. Also to the west was Hatfield Chase, a low lying area of marshes. This meant Lindsey was completely surrounded by water. This led to the popular belief that Lindsey was an Island.