The surface water features shown on this map include streams (rivers and creeks), canals, springs, lakes, and wetlands. The latter are of two main types: swamps and marshes. Swamps are characterized by a tree cover and marshes by a grass cover. Wetlands are generally in stream valleys, along the coast, or adjacent to lakes. Wide interior wetlands are an exception: they owe their existence to the almost flat, essentially featureless geometry of the landscape and the extremely gentle slope of the ground surface. This gentle slope angle, south of Lake Okeechobee, occurs because this part of the state was sea floor, perhaps around a million years ago. Several drainage canals have been dug across the broad wetlands in the southern part of the state.
