Traveling by boat in Vietnam is generally reserved for those who want to explore the Mekong Delta, Halong Bay, or the Perfume River. The slow pace, limited routes, and high costs make it an inconvenient way to get from point A to B. For many riverside or seaside towns in Vietnam, boat rides are a natural attraction, and a great way to get a view of life on, in, or near the water. In northern Vietnam and in the Mekong Delta, ferries are often the only way to get to destinations where bridges have not yet been built or have been destroyed, or to get to islands such as Cat Ba. Bicycles and motor vehicles can usually be brought on board for a fee.
Speed boats that make sea crossings to the islands are notoriously unsafe. Designed for use on rivers, they are often not sea-worthy when the water gets choppy, and the companies that run them tend to take too many passengers. Do some research and make sure you book with a reputable company, or opt for a slower trip on a large dive boat or local supply boat. Life jackets are a legal requirement on all boats; if you are told you can take it off once the boat has passed the checkpoint, you have chosen the wrong company. Ignore them, and keep the jacket on throughout the crossing.
For travel between Cambodia and Vietnam, there’s a speedboat service to Phnom Penh from Chau Doc (a 3–4 hour bus journey from Ho Chi Minh City). Although very few companies service this 5–6 hour transfer, one reputable company that does, is Blue Cruiser. Tickets can be arranged at any of the tour offices in the main backpacker district (Pham Ngu Lao) in Ho Chi Minh City and include bus transportation to the Pier Café boat dock in Chau Doc for approximately $35. Boats depart daily at 7 am and include a stop off at the Vinh Xuong border to arrange visas, before continuing onward to Phnom Penh International Port, which is near the city center.