Goodwin Sands is a 10-mile-long (16 km) sandbank at the southern end of the North Sea lying 6 miles (10 km) off the Deal coast in Kent, England. The area consists of a layer of approximately 25 m (82 ft) depth of fine sand resting on an Upper Chalk platform belonging to the same geological feature that incorporates the White Cliffs of Dover. The banks lie between 0.5 m (1 ft 8 in) above the low water mark to around 3 m (10 ft) below low water, except for one channel that drops to around 20 m (66 ft) below. Tides and currents are constantly shifting the shoals.