The Severn Bore

Well worth a look if the tides are propitious.  Even if it's not the biggest bore of the year the so called 'moderate' ones are quite spectacular, often with lots of surfers.  There are plenty of websites where you can look up the times and size of the bores -- just Google it.  There are also quite a few good locations for watching it, both north and south banks of the river, from Framilode up to Over Bridge in Gloucester; parking is easier at some sites than others.