Hawaii has no legal nude beaches - nudity is illegal everywhere that is view of the public. The mechanism for tolerating nude beaches - at least on this island - is that the police will tacitly agree not to patrol an area. At Kehena, this means that it has become the community's responsibility to push out drug dealing, for example. At Beach 67, it means that the police or Department of Land and Natural Resources, if called in on a fishing violation, sexual complaint, or (yes, sadly) by a tourist with binoculars, will make a halfhearted request for everyone to dress.
Robert Moses State Park is listed as a legal nude beach. It is a TEXTILE beach.
Immediately to the east of Robert Moses State Park is Lighthouse Beach which is designated as clothing optional.The difference is Lighthouse is on federal land while Robert Moses is on state land.
The Fire Island National Seashore in NY Long Island is very nice. You can walk and swim nude. but its too cold now!!
I've gone swimming in the Ocean on LI in early Oct. I've had roses blooming in October. It really depends on the gulfstream I think.