To improve water quality inexpensively by agglomerating a pollutant in the water of a basin, rivers, lakes and marshes, the ocean or the like without damaging a fine sight.

This self-swimming type fish-shaped water-immersed apparatus for agglomerating pollutants is constituted of an underwater self-swimming means having a fish-shaped outer shape and constituted so as to freely swim like a fish in the water of a basin, rivers, lakes and marshes, the ocean or the like, a pollutant agglomerating means for taking in water of the a basin, rivers, lakes and marshes, the ocean or the like to agglomerate the pollutants in the water and a position deta detecting means for accurately grasping its own position to prevent straying.