The crossword solution for the term 'challenge to a canoer' is EDDY. An EDDY is a swirling body of water that can be found in rivers and streams. It is often caused by an obstruction in the flow of the water, such as a rock or a bend in the river. Canoers must navigate around eddies in order to avoid being pulled into them and capsizing. Eddies can also be used to the advantage of canoers, as they can be used to slow down and rest.