The Severn Bore makes its way up the river Severn through Gloucestershire. A number of bores travel up the river every year, some big enough to surf.
They are created when the tides coincide with the right balance of fresh and salt water in the channel, the wind being in the right direction and an area of low barometric pressure.
The bore yesterday was a four-star event on a scale where five is the biggest. The largest recorded wave was 9ft high.