There is a characteristic type of Mendip cave, in which there is an initially steep descent, and then a more level stretch ending in a sump as the cave reaches and descends below the prevailing water table. The passages below the water table (which may be accessible by cave diving) often have a loop formation caused by the water flowing down a bedding plane and then rising up a fracture in the rock. Few caves on the Mendip Hills are more than deep or a few kilometres in length, (with some notable exceptions, such as Swildon's Hole which is over long), but a number are complex with several levels of passages which have been abandoned by the water, for example those around Cheddar.