Go to Sihanoukville. Cambodia's only port can be reached from Phnom Penh to the north, or Kampot and Kep to the east. The trip from the capital of Phnom Penh is an easy bus ride straight down an American-built highway. Getting there from the east will require hiring a sharetaxi in Kampot. There are flights available from Siem Reap for those who want to skip Phnom Penh and hop straight from Angkor to the beach.
Pick your beach. Which beach you stay on will largely determine your accommodations. For posh resorts and privatized sand, head for Independence or Sokha beaches. For a cheap stay in the seedy city of Sihanoukville, do Victory Beach. For backpacker central, head for Serendipity Beach. Finally, for the least developed (but also marshiest and most insect-ridden) beach, go down to Otres.
Go snorkeling and SCUBA diving to the Koh Tang Group and Koh Rung Group of islets. This industry is finally taking off in Cambodia, and many of the local sites are in pristine condition.
Check out the mangroves of Ream National Park, only 30 kilometers, about 18 miles, from Sihanoukville.
Party. Sihanoukville is packed with booze, quasi-legal pot (check out the "happy pizzas," because the seasoning isn't oregano), hedonistic backpackers, and lurid prostitutes. People go to Sihanoukville do get into all sorts of trouble, and this is one of the places where you will see obese 50 year old Germans in speedos with a lithe hooker on each arm. Whatever your definition of a good time is, please be safe.
