Other
Ream National Park
A wonderful mangrove nature reserve about 30 minutes driving from Sihanoukville. Take a moto to park headquarters for US$2. From there, park rangers offer walking tours for US$5 or boat tours for US$20 4 people. Call in advance. The organised trips from Sihanoukville can be disappointing, as they sometimes fail to supply a proper guide and the food can be a bit dodgy.
Kampong Pier Nup Lok
The old fishing port. Offers some nice views.
Koh Russei (Bamboo Island)
See the seperate article on Koh Russei for more information.
The town itself doesn't offer much to see.
beaches
The main reason to visit Sihanoukville is the beaches. They are not as crowded as many of those in Thailand, but can be cramped on weekends and holidays. Like many beaches in Southeast Asia, they are covered in a lot of rubbish, but Otres beach is very clean.