One where the fields (EM, B) are surrounding it, which would probable mean it would not be matter.

Hmmmm, likely not any time soon. Remember that the force of gravity is 1E36 times weaker than the EM force. A gravitational wave is essentially space itself stretching and compressing. So like on the ocean unless the wave is crashing against the shore, you will just bob up and down as the wave passes by, surfing no where. Where do gravitational waves crash against a shore? I don't know. So you should probably try surfing on EM radiation first, as this will be way easier. Though it is easier to sail ( on EM radiation that surf on it. Also, you can surf electrons on a plasma wave.

https://en.wikipedia.org/wiki/Plasma_acceleration

http://sail.planetary.org/

There is no net "force" I can see on a point particle being illuminated by a GW. I would also think that the only means of momentum transfer is by scattering of gravitational waves from your board. Good luck with that one. 

Given that the lower the energy of the wave and the longer and faster it moves, the longer your board needs to be (we Santa Cruzan's know these things)... I'd say you need an extremely long one and extremely light weight. Be prepared to spend$$$$4444

   Surely   a gravitational surfboard.  Now the  question   is  where  are those  sold?

Max,  Gravitational waves do not produce a displacment of the center of mass of an object.  A gravitational wave propagating in the Z direction will convert a sphere into an oscillating ellipsoid which alternately stretches and shrinks the X and Y directions without a net volume change. Also, the gravitational wave propagates at the speed of light, so you are never going to move this fast.  

More  seriously, I think, in contrast with  some of the   comments   made  before,  that    in principle a gravity wave  would indeed  propel  an   appropriate  kind of   surfboard. Think  for instance of a  gravity wave like the one   recently detected in LIGO  but  instead  of looking at it from the  Earth,   looking at it from    nearby the   colliding black holes  (say at  a few  million  kilometres) .  The  gravity wave  would  have a huge  amplitude, and    thus a large  enough  surf  board ( in fact any object)    floating   in  empty space  will deform  due to the passing of the  wave.  This  in  turn will lead to the objet to  develop  an oscillating  quadruple moment in its  mass distribution and   thus  to emit  gravity waves in  many  directions.  Those   secondary   gravity waves will   interfere  with the original   gravity  wave,    leading to  some    nontrivial   patterns   f constructive   and  destructive  interference that  will result  in  3- momentum  being  carried  away from the  board  in an  anisotropic  fashion.   This  will result in a net  impulse  transferred to the surf board. Symmetry considerations   clearly indicate that such impuse  will be along the direction of propagation of the  original gravity wave.

So  yes ...  get a large  enough, massive      and   readily reformable object to  play  the role of your surfboard... get copse enough to  a   couple of colliding  black holes and you will   be ready.

Good  surfing .. mates... 

Since we have all drawn to the conclusion that a body in the line of path of a gravitational wave will experience a displacement away from the source of the gravitational wave. This should be the source of Dark energy.

It would be interesting to see the interference of 2 gravitational waves.