Contrary to popular people belief non-lewd, non-sexual nudity on Hawaii's beaches is not illegal. However, nudity of any kind is forbidden in state park beaches, such as Honokohau Harbor Beach.
That being said, there are plenty of beaches (the vast majority, really) on the Hawaiian Islands that are not located in state parks, so feel free to ditch your bathing suit in favor a birthday suit instead.
Big Island of Hawaii
Hawaiʻi (also called the Big Island) is the largest and the southeastern-most of the Hawaiian Islands.
- Honokohau Harbor Beach is located in the Kaloko-Honokohau National Historical Park on the Kona Coast, north of Honolokohau Harbor off of Highway 19. The north end of this yellow sand beach is a popular gay beach. Since it is a federal park, the no nudity law is enforced by rangers patrolling the area. However, it remains a popular nude beach despite the illegality.
- Kehena Beach (Dolphin Beach) is in the Puna district (Hilo side) off Highway 137 near the Mile Marker 19. This is a well shaded black sand beach protected by steep cliffs and tall trees. Swimming can often be hazardous due to rough current and high waves, but it is popular among local residents.
- Steam Vents located near Hilo at Mile Marker 15 of Highway 130, features clothing optional steam baths in natural caves. Although it is a private property, the owners allow the public to use the space. A large house nearby acts as a clothing-optional guesthouse called "Steamvent Guesthouse."
Geologically, Kauai is the oldest of the main Hawaiian Islands and is nicknamed "the Garden Isle" due to the tropical rainforest that covers most of the island.
- Donkey Beach is located 7/10 of a mile north of mile marker 11 on Highway 56 and is not visible from the road. Access to the beach is via a path through an old sugar cane field on private property. Not too long ago, Donkey Beach was known as one of Kauai's best nude beaches, but once a mainland developer took ownership of the beach, security guards were hired to enforce a no-nudity policy. In short, it's not worth the risk.
- Secret Beach, also known as Kauapea Beach, is accessed by hiking a trail at the end of a red dirt road off of Kalihiwai Road, which is found about a half mile north of Kilauea on Route 56. It is known for being Kauai's premier nude beach, although it's rare to see more than a couple people sans clothing. Secret Beach is a long, yellow sand beach which offers beautiful scenery. Swimming during winter is not advised due to high surf, but at other times of the year, excellent snorkeling can be found here.
Maui is known as a nature lovers island with incredible waterfalls, bamboo forests, and plenty of exploring to be had at Haleakala National Park.
- Little Beach at Makena (Pu'u Ola'i Beach) is adjacent to Makena Beach (Big Beach) but is inaccessible by car. To get there, drive to Makena Beach (located a few miles past the Maui Prince Hotel) along Makena Ala Nui road, park at the paved parking lot, and walk to the beach. Theft from cars is common here, so remove all valuables from your car, and possibly invest in a beach lockbox. At the northwest end of the beach, there is a path up the lava rocks that takes you over the outcrop to Little Beach. This is, perhaps, the best spot in Hawaii for nude sunbathing. The swimming and snorkeling are also excellent.
- Red Sand Beach in Hana (Kaihalulu Beach) is one of Hawaii's prettiest beaches, but it is difficult to reach. The remains of a caved-in cinder cone have created the beautiful cove in which this crescent-shaped beach is found. You will have to drive to the Hana Community Center on Ua Kea Road, next to the cabins that are a part of the Hotel Hana Maui. At the south end of the Community Center is a path that passes by an old cemetery. This path crosses to the shoreline and up and along the face of the outside of the cinder cone. The path is narrow and the footing is poor, but at the end of the path, you'll find the Red Sand Beach. The water is calm and clear, and perfect for swimming or snorkeling. This is a very small beach, but one which should not be missed.
Oahu is the most populated of the Hawaiian Islands and the island most visited by tourists. On a nice day, most beaches are crowded with locals and tourists alike; therefore, its beaches are not ideal for nude sunbathing. Though you can take your chances at beaches like Polo or Kahuku, guards do patrol more frequently.
Molokai is the least visited of the main Hawaiian Islands (not including Kaho'olawe which is closed to the public).
- Papohaku Beach, which is one of the world's longest beaches almost guarantees a private, secluded area for uninterrupted nude sunbathing bliss.