Gloucestershire daily witnesses a tidal wave, known as the Severn Bore. Because of the converging shape of the Severn Estuary, and its rising river bed, a tidal wave sweeps up the estuary twice a day. The estuary experiences the second highest tide anywhere in the world. The tides are affected by the lunar cycle and on certain days in each month the phenomenon will be more impressive than others. In the most favourable conditions, such as high tide and a following wind, the bore might form a wall of water up to 2 metres in height.

The bores are rated on a five-star system, the most spectacular being five stars. The arrival of the bore can vary by thirty minutes either way of the given time. Viewing normally takes place at one of three places; Minsterworth, Stonebench or Over. The bore, as such, does not continue beyond Gloucester because of weirs on the two channels of the river.

As the bore passes, you will see not only the wall of water but a large number of surfers and canoeists who come to ride the bore. Most noted of these is the man who holds the world record for long-distance surfing.

After the bore has passed by, there is still a rise in water level for an hour or more. Be careful not to get caught out by the rising waters of the River Severn. Spectators and their transport have been cut off by the tide in the past and have needed rescue. Stonebench is particularly notorious for this where the road runs close alongside the river.