Check this game out:
I tried to copy it to post it over here. Read the instructions and see how far you can get with your 40 strokes. All about using the minimum amount of strokes for the runners that come. Pick the best ones and go the furthest. Like Mikeman explained, look for the trough, not the wave.
My Best so far is 680m in 40 strokes. Let me know how many you do.
www.ocpaddler.com/game