A natural phenomena - a wave up to 2 metres in height which sweeps up the river Severn at up to 16 Kmh. It is dependant on the tidal conditions and is produced because of the shape of the Severn Estuary and reaches as far as Gloucester. There are keen followers who will surf it or canoe it whenever possible - the Bore Riders. It is one of 8 in Britain and only 60 in the world.
Shropshire folklore says that Sabrina, a water spirit lives in the river and causes the bore wave which she rides accompanied by salmon and dolphin. One of three sisters who lived in the Black mountains and decided each of a different route to the sea - Ystwith, Wye and Sabrina (Severn).
The other well known bore in Britain is the Trent Aegir.