Shark is my fresh take on conventional street bikes.

The idea is to make them more maneuverable and agile in turns so that the user doesn't have to give away the pedal force s/he has already built up when entering corners.

How?
By allowing the rear wheel rotation perpendicular to the ground....imagine the tail of a shark underwater when it changes direction.
The key difference between any other bicycle and Shark is how it turns.

Let me explain how.
The rear wheel and the chain drive (or belt drive for that matter) are integral and connected indirectly to the rest of the body. This allows the rear wheel to rotate along Z-axis. This rotation (better understood through illustration) thrusts the bicycle in the turn with respect to an instantaneous center closer when compared to a conventional bicycle.

When the bicycle leans for making the turn, rear wheel will have the tendency to scrub and align in a different angle because of the slip generating at the ground patch. The user will have his feet planted on the pedals and s/he can control this according to the turn. Like how a skier would during turns.
During straights Shark will behave like any other bicycle.

Advantages?
People rely on bicycles a lot...A LOT. And it is a big deal when a product saves them seconds on a commute.
Our cities are getting smaller and roads crowded. I don't have to furnish numbers to prove that statement. Well in that scenario, a mail deliverer can significantly save his/her time through traffic. And that's just one example. I'm sure people will find tons of other reasons.

And if that's not reason enough, riding Shark would be tons of fun. It is much more engaging and requires much more user involvement, it invokes emotions. Riding conventional bicycles has become mundane, it's almost automatic and habitual.
On the other hand, Shark would need the user to control its rear wheel like a sail of a yacht.