Phnom Penh's restaurant scene has grown enormously over the past two decades. The street food remains exceptional and almost absurdly cheap — fish amok, lok lak, kuy teav noodles, and num banh chok (rice noodles in green fish curry) cost a dollar or two at any market food court. For sit-down meals, BKK1 and the streets around the Russian Market are the densest clusters, with everything from refined Khmer to Korean, French, Vietnamese, Italian and Japanese.
The river is not a major source of seafood — most fish you eat here is from the Tonle Sap or imported from the Gulf of Thailand. Cambodian cooking leans on freshwater fish, pork, beef, and bright fresh herbs. Try Kampot pepper crab if you see it, and seek out a proper bowl of num banh chok at breakfast time.