(Listing updated 6 months ago.)
There is an unofficial nude beach located at the base of the Diamond Head Light house. The beach is located just off Diamond Head Road, just below and to the left (east) of the lighthouse. There is ample parking on the road. I parked at the top of the hill and walked down a nice, paved walk path to the beach. There was a group of windsurfers at the bottom of the walk path. I turned west and walked about 100 yds and found a nude bather. I walked another quarter of a mile and found the end of the nude beach. This is an old lava flow and the beach is not the greatest for swimming. However, you do get to work on the all-over tan.
(This listing was originally from http://graygay.com/.)