The Big Island is the youngest of all the islands completely emerged from the ocean, and because of that, it does not have the extensive natural white sand beaches that the other islands have. It takes millions of years to make a white sand beach, but only a few hours to create a glistening black sand beach of which the Big Island has several. Many of the beaches on the Big Island are composed of mixtures of lava rock, sand, pebbles and stones and may or may not be suitable for swimming or snorkeling. But even given this, the Big Island has some of the best swimming and snorkeling beaches in the State, and also some of the most unusual beaches. The following is a smattering and is certainly not all-inclusive.
There are some beaches and beach areas that are still somewhat remote. This is changing as developers move in and build resorts next to the once isolated patches of sand. One of the few beaches not currently slated for development, although Bishop Estate, the landowner, could change its mind, is Makalawena.
Most of the newest black sand beaches are on the windward side of the island. And one, the black sand beach at Kaimu, was the most famous black sand beach in the world. It was destroyed in a 1990 lava flow. You may see remnants of it if your travels take you to Puna. Please do stop at Punalu'u Black Sand Beach as it was created by the explosions of lava as it entered the sea and, unlike on other islands, has not yet been eroded by the sea.
Kekaha Kai State Park is very lovely with at least two swimming areas on the main beach and a lovely very private beach a short walk along a path to the North.
Beach camping is a local habit on the Big Island. Wherever you go, no matter how remote you think it is, expect to find other people. All of remote areas on the island are known to the local residents. Residents will "four wheel it" to spots that most of us would think impossible to travel over by vehicle.
Hupuna State Park is one of the largest white sand beaches on the island and easy to get to. All beach amenities can be found here. Restrooms, showers, campsites, lifeguards, food and drink, tables and access for the disabled.
The beach that I often go to is the Old Airport State Park, right around the corner from downtown Kailua-Kona. It's got tide pools to soak in, nice sand to lie in, and even a jogging trail. The beach is long with pavilions, restrooms, tables and shade trees, and it often is not raining there when it's raining all around town. Swimming is tough, but the public pool is right next to it. It's a beautiful pool and it's free.