Velosub - human-powered underwater vehicles

How efficiently do you swim with fins?  They're a big help over using plain naked human feet but what if you could translate your leg power into turning a propellor. 

The Velosubmarine does just this, allowing snorkelers and scuba divers to pedal along at up to 3 knots.

Based in Paris, France the Velosub company offers the eponomous Velosubmarine for 950 euros and also has a nice looking one person wet sub.   Hopefully these will be turning up for trial in resorts around the world.