5 miles, on a surf board - Tidal bore surfing is limited to about 100 rivers. This short video from the Cook Inlet, Alaska may cause you to buy a board. (previously)
In May of 1940, "Mad Jack" Churchill became the only man in WWII to record a kill with a longbow. [more inside]
Bore Riders are a strange breed of inland surfers, catching periodic tidal surges (pic) that can carry them for miles upriver. Surf the English countryside, France's Bordeaux region, the freezing waters of Alaska's Cook Inlet, the Amazon jungles, or China's Silver Dragon, the largest tidal bore in the world.