To the east lay the flat marshlands of the Isle of Grain.
The Thames was once a much broader, shallower river with extensive marshlands.
Marine and aquatic life have suffered as a result of these poisonous chemicals contaminating ocean beds, wetlands and marshlands.
With the drying up of this channel and the closing of Sandwich harbour in the 16th century, the present marshlands or level to the south and west of the isle were left.
The name of Alkmaar, which means "all sea," first occurs in the 10th century, and recalls its former situation in the midst of marshlands and lakes.