Cat Ba Island is 45km east of Haiphong and 20km south of Halong City. Be aware that there are several piers on Cat Ba Island. Most handy is the jetty directly in front of Cat Ba town from where the hydrofoils to Haiphong depart. A second popular one is at Ben Beo, about 2km from Cat Ba town where most of the tourist boats berth. The other pier is at Phu Long, 30km from Cat Ba, where boats from Cat Hai arrive. At Phu Long, motorbike drivers wait to whisk passengers from the ferries to town (or the 15km to Cat Ba National Park) for about 50, 000d. There is also a public bus that meets the boats, but this takes longer to get across the island.
The best option for independent travellers is the hydrofoils linking Cat Ba directly to Haiphong. These air-con rockets reduce the journey to just 45 minutes. There are several companies running the route, with three departures a day in the high summer season and just once a day the rest of the year. Summer season services depart between 10am and 5pm. Transtour (888 314) runs the Mekong Express (100, 000d, 2.45pm departure), which is the safest and most comfortable option. Tahaco (031-374 7055) has smaller hydrofoils, which are cheaper at 70, 000d and depart at 3.15pm. There are no longer hydrofoils operating to Halong City.
The easiest way to get from Halong City to Cat Ba is to hop on the tourist boats (100, 000d, five hours) that leave several times a day. This is less organised going in the other direction to Halong City, but your guesthouse or hotel should be able to hook you up with a boat going that way.
There are also plenty of slow, chartered tourist boats making the run from Halong City to Cat Ba Island; check with the cafés and travel agencies in Hanoi about tour options. Such trips generally include all transport, accommodation, food and a guide, but double check to be sure.
An alternative way to reach Cat Ba town is via the island of Cat Hai, which is closer to Haiphong. A boat departs Haiphong and makes a brief stop in Cat Hai on the way to the port of Phu Long on Cat Ba Island. It is also possible to drive a motorbike or car to Haiphong, from where you can get the ferry to Cat Hai, then drive 15 minutes across the island to a pier from where you take a ferry to Phu Long. This accounts for all those surreal traffic jams during the summer season. A bridge is under construction to Cat Hai which will make Cat Ba even easier to reach by vehicle.
There are also direct buses from Hanoi to Cat Ba town. Hoang Long bus operates four services daily to Cat Ba (120, 000d, four hours) from the Luong Yen bus station. However, it is just as easy to use the bus-hydrofoil combination via Haiphong.