and man, he do crowd a paradise…

The Severn Estuary, which empties into the Bristol Channel, has the second largest tidal range in the world — about 49 feet (15 m), exceeded only by the Bay of Fundy; and during the highest tides, the rising water is funneled up the estuary into a wave that travels rapidly upstream against the river current. The largest bores occur in spring, but smaller ones can be seen throughout the year. The Environment Agency publishes timetables and predictions of bore heights on its website. Being the onset of the flood tide it is accompanied by a rapid rise in water level which continues for about one and a half hours after the Bore has passed. The Severn Bore is not a self-reinforcing solitary wave or soliton, but rather a shock wave which is formed because the wave is travelling faster than the wave speed in water above the Bore (see tidal bore for more details).

The largest recorded Bore was on 15 October 1966, when it reached a height of 9.2 feet (2.8 m). http://en.wikipedia.org/wiki/Severn_bore