The term 'River Wave' is a combination of two words, 'BORE' and 'Wave'. A BORE is a large wave that is created when a river's current meets an obstruction, such as a rock or a sandbar. The wave can be up to several feet high and travel upstream for some distance. It is often seen in rivers with strong currents, such as the Amazon River. River waves are popular among surfers and kayakers, who use them to ride upstream.