Human-powered airboat

Back in the early 90s, MIT's Prof. Mark Drela created a motor-less hydrofoil known as the Decavitator. Using nothing but his own leg power to turn the craft's 10-foot (3-m) air propeller, he got it up to a speed of 18.5 knots (21 mph/34 km/h), breaking the human-powered water speed record in the process. Inspired by the Decavitator, aerospace inventor Russell Randall created his own pedal-propelled airboat called the Seahorse – and you can now buy one of your own.

Randall first started producing Seahorses in 2001, but stopped to refine the design and perform more on-the-water testing. An unsuccessful Kickstarter campaign followed, but he is now resuming production on an improved incarnation.

Instead of paying for a permanently-attached pedaling platform, users just mount their own bicycle on the trampoline-style deck of the Seahorse. As they pedal, they turn the craft's air propeller, pushing the boat forward. If they wish, they can pay a little extra for the addition of a more traditional water propeller which has only two moving parts, and allows the craft to go upwind in breezier conditions ... although it also slightly increases the chances of getting fouled in aquatic weeds.

When they get to their destination, users then have the option of putting the wheels back on their bike, and using it to get around on the local roads

According to Randall, the Seahorse is faster than a traditionally-paddled canoe or kayak, plus it can move backwards simply by reversing the propeller's pitch via a handlebar control. Users can also install an optional sail and use it as a regular catamaran, without the bike.

Two main versions of the Seahorse are available. There's a 14-foot (4.3-m), 25-lb (11.3-kg) polyethylene model that goes for US$$3,900 with the air propeller, or $4,400 with both air and water props. The longer 18-foot (5.5-m) version is made from fiberglass, and goes for $4,400 with an air prop or $4,900 with both. Potential buyers who don't want to spend quite that much can instead go for a water-prop-only setup, priced at $3,000 for the 14-foot boat and $3,500 for the 18-footer.

Both versions fold inward (the pontoons come together), allowing them to be carried through a standard doorway.

You can see one of the Seahorses in use, along with a funky waterproof quadcopter, in the video below.