From Phnom Penh, ferries called "bullet boats" travel along the Tonle Sap to reach Siem Reap and Angkor; they also ply waters between Sihanoukville and Koh Kong. 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 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.