PROBLEM TO BE SOLVED: To provide a water area structure capable of improving water quality.SOLUTION: The water area structure to be installed in a water area includes: an internal space 11 filled with sandy soil so that a detritus feeder which ingests and decomposes detritus can grow； an upper opening 12 which is in contact with a water surface of the water area and is opened toward the water area so that the detritus feeder can go back and forth between the internal space 11 and an aquatic space of the water area； and a lower opening 13 which is opened toward the water area so that the detritus feeder can go back and forth between the internal space 11 and underwater of the water area.
