A water vortex created in a tank at Techniquest, Cardiff, Wales. Water vortices have been associated with turbulent tsunami flow. It has been argued that a vortex may act like a 'drill-bit' if armed with pebbles and small boulders at its tip, drilling into bedrock forming a circular erosion scar. See E. A. Bryant (2008) Tsunami: the Underrated Hazard (2nd Edition, Praxis Publishers, Chichester) for further details. An example of a possible vortex eroded hollow occurs in bedrock in the intertidal zone at Ogmore, Glamorgan (UK), as suggested by E. A. Bryant and S. K. Haslett (2007) Journal of Geology.