Koh Rong has many unexplored beaches.
Some are white sand beaches. Many are rocky beaches. They're all fun. (just don't step on any sea urchins)
Except for Koh Rong Village's Beach, all the other beaches are very, very quiet.
Koh Rong Village is a group of about 35 bungalows and restaurants wall to wall on the beach. The bungalows go up the hillside and are quite peaceful in the jungle. However, at the beach, it's party time in the afternoon and night, sleeping time in the morning.
You can stay at one of the beach bungalows on the quiet 98% of the island, and when you're bored, you can take a walk (or boat) to Koh Rong Village.
You can see the coast of SihanoukVille from Koh Rong Island. Also, many other close by islands.
Many of the beaches have paths cut out in the jungle that you can use to explore by foot.