I use PVC pipe to get my N5.2 on and off the beach. Get three 10-footers of 3-4". I can easily move my boat around with these. At low tide, there is quite a step up to the normal beach area where the PVC will hang up in the sand, but the boat will still slide fairly easily on the round surface until I get it to the flatter area. I'm not sure how well this will work in the rocks you talked about. You may need to go with a bigger diameter pipe.

-Rob
Panama City
Nacra 5.2