The term 'sump' is used to refer to a variety of water-holding structures. A SWAMP is a wetland area that is filled with water, usually shallow and often marshy. A BOG is a type of wetland that is characterized by acidic water and spongy soil. A RESERVOIR is an artificial lake created to store water for human use. A DRAIN is a pipe or channel used to remove excess water from an area. Finally, a PIT is a large hole in the ground, often dug for the purpose of collecting water.