The waters off the coast of Sihanoukville are still unspoiled with an abundance of marine life. Giant clams, sea oysters, gorgon and fans 10 meters. There are more than 20 islands and miles and miles of coral reefs that can typically be reached in one day by boat.
The Kompong Saom Group
The Kampong Saom group has very good beaches and diving. Koh Pos (Snake Island) is a short 800 meters off Victory Beach. One km west is Koh Koang Kang, which has recreation offerings like shallow rocky reefs for great snorkeling and two beautiful beaches.
The best island has to be Koh Rong Samloem, which can take up to 2 1/2 hours to get to. You can see a beautiful heart shaped bay as you approach. You will find around 9 beaches on this island, even some sheltered ones on the northern side where you can see Koh Kon. Both islands have rocky reefs that contain an abundance of marine life in both deep and shallow waters.
From November to February it is better to visit the sheltered Ream group of islands, as the wind is too strong around the Kampong Som Group. They are about 1 and half hours away. The shallow waters can have limited visibility. Koh Khteah, Koh Chraloh and Koh Ta Kiev are best for snorkeling. Giant mussels can be seen on the north side of Koh Ta Kiev Island.
Koh Russei(Bamboo Island) can be camped on if you want to overnight it as it has a great beach on the northeast side, and now has a small selection of basic beach bungalows.
By far the best scuba diving area is Koh Tang, Koh Prins and Poulo Wai but they are 7 hours away to the southwest. With excellent visibility in waters to 40 meters that are teaming with marine life, Kot Tang is described as a sea lovers' paradise. Koh Prins has some shipwrecks and a downed US helicopter at 35 meters down.
Many of the Islands around Sihanoukville are being purchased for development, and may not remain this pristine for long. So take the opportunity to dive the site before it changes forever.