The Gills press the oxygen-weak water out as a result of openings in the sides with the pharynx. Cartilaginous fish have numerous gill openings: sharks generally have 5, in some cases six or seven pairs; they normally should swim to oxygenate their gills. Bony fish have an individual gill opening https://maps.app.goo.gl/9y4LfCmrsyYSbzTo6