Here is the address for the secure parking place.

Moon Landing RV Park & Marina‎

4105 Watts Bridge Road
Cross Hill, SC 29332-5049
(864) 998-4292‎

The island is very near there.
N 34.23501
W 081.98487

As I recall, my GPS said I was at the address about 3 miles early.
I had to call them.