"In perhaps one of the great ironies of human civilisation," writes Brian Kaller, "mechanical devices to truly magnify human power came along as soon as we didn't need them." Kaller's article, "The Hidden Potential of Bicycles," is well worth a read.

To Kaller's point, bicycles came around in the late 1800s, and the motor car followed soon after. This makes it easy to overlook that bicycles are, in Kaller's opinion, "the most efficient method of using our bodies, allowing us to attain higher machine speeds for longer than we would on muscle power alone – and without using any more fuel or causing any more weather to go haywire."

Speaking of bicycles, remember industrial designer Josep Rubau's aquatic bicycles?

While those transform a pedaling motion into forward thrust in water, a French invention called the Seabike does the same—but gets rid of the middleman, so to speak. The Seabike is essentially a pair of pedals driving a propellor, and is meant to be worn by swimmers.

"It's simple! You pedal, the propeller turns."

"SEABIKE is a portable water bike that is attached to the belt (included with the transport bag). Pedaling it helps you travel across long distances in freshwater and saltwater alike. It allows you to cover distances of several kilometers with moderate energy consumption. The speed of movement in nominal mode is 1 m/s, the maximum speed is 2.2 m/s."

As you can see, this dude is indeed cruising:

Some underwater footage that gives you a closer look:

Enter a caption (optional)

The Seabike base model runs €290 (USD $309). The Seabike Pro version, which features a quick-release propellor and a ballast weight to adjust its buoyancy, runs €370 (USD $395). The Seabike Premium is the Pro, but made of titanium; they don't say what the other versions are made of.