Tides progress up the Severn River in SW England as a tidal bore moving faster than 6 m/s. During spring tides, the leading edge of the bore can be up to 2 m high, taking more than an hour to travel from the lower portion of the river to past Gloucester. This is sufficient to attract surfers from around the world. The North Atlantic amphidromic system interacts with the broad continental shelf around the U.K. to produce a complicated field of large tidal ranges. This forces a twice daily standing wave along the Bristol Channel, that further amplifies the tidal range toward the back of the Channel and the mouth of the Severn River. High tide is effectively a very long wave that moves against the out bound Severn River flow, so the leading edge sharpens, forming a bore. The shape of the leading edge varies between a smooth wave and a breaking wave. The presentation will include two short videos of the bore.