Speaking of saving energy, I came across a boat that does just that. I don't know who needs a solar boosted pedal boat (although I would like one), but a design concept for one exists nonetheless. The boat features a center cockpit where at least four passengers can sit, alternating pedaling duties in 2 person shifts. When you get tired, switching to solar power can help lighten the load. I could possibly see these at amusement parks or state parks. Somewhere where families can go and enjoy their day with a nice solar powered boat ride around the lake. Sounds nice, right?
I'm not sure if this concept will ever see the light of day, but in a world filled with non-solar powered pedal boats, it would be a welcome transportation.
Take a look here for pictures and a video.