Acilius canaliculatus is a species of water beetle commonly known as the smooth diving beetle. It is characterized by its elongated body, ranging from 10 to 15 millimeters in length, and its shiny black or dark brown coloration. This species is well-adapted for an aquatic lifestyle, with flattened legs and a streamlined shape that allows it to swim efficiently. Acilius canaliculatus can be found in freshwater habitats such as ponds, lakes, and slow-moving streams, where it feeds on small invertebrates and detritus.