Since you have posted it in critique… the shot is dark and you are losing detail due to you having under exposed the shot. A little attention during post-processing could easily make a huge improvement on that. The focus doesn’t seem quite right, this is either due to shutter speeds not being fast enough for the length of zoom that you were using and thus some camera shake has been introduced, or quite simply that the focus is slightly off. For an image of this size again if you had given it some attention during post processing, it could have brought much more detail out and drawn us into the picture, as it is currently it’s a bit flat and lifeless.
The framing of the shot is wrong too, you have much more space behind the surfer showing where he has been. With all sports and with nature, it is generally accepted that if you are having free space around your subject it should be in the direction that they are moving or looking. Yet again this could be corrected during processing with a crop but it is better to learn that and try to apply it during the shoot.
All my points above could be applied and this image would be far stronger, there is definitely a good shot in there fighting to get out, you just need to spend a few minutes working with it to get a great result.
HTH
