This is for an easy entry level design that is is very rewarding because it will move through the water with its paddle propeller. Just cut the boat and the propeller, slide the propeller together, put a rubber band on the boat, spin the propeller backwards as much as you can then drop it in the water to let 'er rip!
Cut the main boat body out of either 6mm or .25" wood. Also cut the paddle flipper pieces out of 3mm or .125" wood.
Assemble the paddle prop by sliding the notches on each side of the two pieces together.
Place a rubber band around the two notches on the back side of the boat. Pictured is a 3" rubber band.
Next weave the assembled paddle into the rubber band in a way that the rubber band is freely holding the paddle.
Now that everything is assembled you can spin the paddle backwards (towards you) until you get the rubber band spun tight. Holding the tight paddle set the boat in the water and let go of the paddle which will allow the boat to move!