River Arth
 The River Arth is a small river that emerges in the hills near Bethania Ceredigion Wales which runs west for 15 miles (24 km) and discharges its waters into Cardigan Bay at Aberarth. Despite its small size it is one of the few rivers in Britain which has a bore when the incoming tide cause a tidal wave to run upstream. The Arth bore is only a few inches high and it runs only for a short distance upstream.