Final answer:
Canoeing near the shore upstream is beneficial due to the slower water flow caused by friction, whereas, downstream, it's better to be middle-river where currents aid faster travel.
Step-by-step explanation:
When paddling a canoe upstream, it's advantageous to stay close to the shore because water flow is typically slower there due to friction between the water and shore. On the other hand, paddling downstream, it may be better to stay near the middle of the river where the current is stronger, allowing for an easier and faster journey with less paddling effort required.
Being near the shore while going upstream allows canoeists to avoid the stronger currents that are present in the middle of the river, whereas being near the middle when going downstream enables taking advantage of those same strong currents to speed up the trip. It's all about effectively managing the water conditions to make canoeing more efficient.
These principles are part of a greater understanding of navigation and how to work with natural aquatic environments to travel effectively, both upstream and downstream.