Boats do travel from Ho Chi Minh City to Phnom Penh, but they take three days and are a sightseeing option rather than quick A-to-B travel. From Phnom Penh, ferries called "bullet boats" travel along the Tonle Sap to reach Siem Reap and Angkor; they no longer ply waters between Sihanoukville and Koh Kong, however, so the only way to go is by road. You can buy tickets from a tour operator, your hotel's concierge, or at the port in Phnom Penh. Bullet boats, though fast, can be dangerous. Smaller (but noisy) ferries travel daily between Siem Reap's port and Battambang, on the Sangker River. Ask about water levels before booking a ticket; in dry season the water can get so low the boat may get stuck for hours at a time. For those who like to sit atop in the fresh air, take lots of suntan lotion.