This is a strange town. It serves 2 purposes, firstly it's where the boats take you to the islands (mainly Koh Rong) and back. Secondly it's a seedy town full of sex tourists and people getting absolutely smashed every single night. I don't think I've ever seen a place where the sex tourism is so widespread and accepted. I stayed for one night and had really quite a fun night out with a friend from Crusoe Island. We were pretty happy about our room with a shower and A/C after 4 nights on Koh Ta Kiev (see below), especially for only $7.50 each. Then we had some buckets and danced a lot on the beach. However that doesn't mean it's a place worth visiting. Of course, this mainly applies to the central part of time, Serendipity Beach. Otres and Otres 2 are much more relaxed beach areas which are apparently really nice (though not as cheap).
Tip: Get drunk and then leave quickly.
Accommodation
Monkey Republic
Good location, nice little room, $15 for a twin, included free beers.
Food
Sandan
Sister restaurant of Friends and Romdeng in Phnom Penh. Local food in a fine-dining style at cheap prices. Some dishes can be ordered as a half portion so you can try more things. Oh and it's all for a good cause. Recommended.
Nightlife
Serendipity Beach
Everywhere really. The real fun doesn't start until around midnight down at a few of the beach clubs. Dance and drink buckets!
Sights & Activities
Food
Please use my Cambodia food guide which has all of my favourite places and dishes for the best food in Sihanoukville.