The ocellate river stingray (Potamotrygon motoro) exploits vortices of sediment to bury into the substrate

Particle image velocimetry and video analysis were employed to determine the pectoral-fin mechanism used by the stingray Potamotrygon motoro to bury into sand. Rapid oscillations of the body and folding motions of the posterior portion of the pectoral fin suspended sediment beneath the pectoral disc and directed vortices of sediment onto the dorsal surface, where they dissipated and the sediment settled. Body coverage was increased by increased fin displacement and speed and also by the occasional collision of vortices that redirected sediment flow towards the head and tail.