The moors and levels formed from a submerged and reclaimed landscape. The area was prone to regular flooding, particularly before the sea defences were enhanced at Bridgwater in the early 20th century. The area broadly corresponds to the administrative district of Sedgemoor but also includes south east Mendip.
Much of the area is at, or only slightly above, sea level, so until it was drained in the 17th century it was a marsh that was frequently flooded by the sea. The area was settled by the Bronze Age, with the population living on artificial islands connected by wooden causeways on wooden piles, supporting themselves largely by hunting and fishing in the surrounding marsh. Several towns were also built on the natural 'islands' of slightly raised land, including Brent Knoll, Glastonbury, and the low range of the Polden Hills. It's easy to see why the area acquired a number of legends, particularly of King Arthur and his knights, who may have based his court at the hill fort at Cadbury.
Although now mechanically drained by a network of drainage channels, known locally as "rhynes" (pronounced "reens"), the levels are not as intensively drained or farmed as the East Anglian fens (historically a similar area of low marsh), and are still liable to flooding in winter. Consequently the Levels retain a rich biodiversity and contain several Sites of Special Scientific Interest. The "Somerset Levels and Moors" is also a recognised Environmentally Sensitive Area.
Flowing through the Levels, the River Parrett provides a source of eels (anguilla anguilla) and elvers during January throught to May. Historically the Moors have also been used for peat extraction and though much reduced at least one large firm still operates on the levels and peat lorries remain a common feature of the back roads.