Football fin

I came across a  football fin and would like to use it in my 10 foot longboard. 

Can anobody explain the rationally under this design?

Thanks in advance

If you are reffering to an elliptical fin, read this wiki page:

With classic analytical aerodynamics, one can proove that for subsonic flows, an elliptical wing shape is the most efficient.

I think this is what he was referring to,