Crystal Voyager surfboard

Ahoy Swaylockians, I just recently watched the 1973 classic Crystal Voyager.  The surfboard that Nat Young uses in the film is really interesting.  It has a triangular singlefin keel.  Nat Young really rips it up on that board.  I had never seen anything like it before.  Does anyone here know anything about the history/ride characteristics of that fin design?  

 

I just realized that there are a bunch of other threads on this exact topic.  Sorry yall.  Shoulda checked first.