Each type of water: whether expansive oceans and lakes or meandering streams and rivers – have their own unique hazards that challenge the paddler. Some are natural such as currents, rip tides, rocks, reefs, narrowing channels, winds and myriad natural obstacles (surface and submerged). Other hazards are man-made (dams, weirs, spillways, structure abutments, stump fields, barge wake) that can also cause the flowing waters to act in ways that can be very dangerous to paddlers of all skill levels. Of these, arguable none present the diversity and intensity of hazards as do the flowing channels of water we call rivers.