Paddleboats are fun! In light of faster designs using rigid, cardstock sails, a paddleboat may not win in the speed category. The design category is a better target for a good looking paddleboat.
Paddleboats convert the force of your breath to a direct push on the water. You focus your breath on the veins of its paddle. The paddle turns in response and pushes water behind the boat by means of the same paddle veins. A paddle leverages the force of your breath to push directly on the water. Watch out, you'll probably get wet!
Because a paddleboat has moving parts and must be bulkier than other regatta boats (but not heavier), it is more difficult and exacting in design and construction. There are challenges in finishing this type of boat as well.
In terms of design, a paddleboat is best constructed on a catamaran type hull or a flat hull with the paddle housing making up the back of the boat. The flat hull is not as stable as the split catamaran hull, but it can offer more flexibility in design.
If you design and build a paddleboat well and practice good blowing techniques your paddleboat should be able to race the 10 foot regatta rain gutter in about 10 seconds. Though it may not win, it is a great crowd pleaser and demonstration of physical process.