Most Indonesians choose to travel between islands by boat, either on the state shipping line, Pelni, or on anything from cargo freighters to tiny fishing vessels. Pelni currently operates about twenty passenger liners , which run on two-week or monthly circuits and link Java with ports on all the main island groups between Sumatra and Irian Jaya .

The vessels carry 500 to 1600 passengers each, are well maintained, as safe and punctual as any form of transport in Indonesia can be, and the only widespread form of public transport that offers any luxury. Comprehensive timetables for the whole country can be picked up from their head office in Jakarta; provincial offices should have complete timetables of all the ferries serving their ports, which you can copy or take away. Tickets are available from Pelni offices three days before departure, but as there's a big demand for cabin berths it's best to pay an agent to reserve you these as early as possible. You can only buy tickets for services which depart locally.

Accommodation on board is usually divided into two or four classes. All are good value, and include meals ; cabins also have large lockers to store your luggage. First class consists of a private cabin with a double bed, washroom, TV and air-conditioning - about US$15 a day is standard. Second class is similar, but with four bunks and no TV (US$10); third class is a six-bunk cabin without the washroom (US$7.50); and fourth class is just a bed in a dorm (US$5). If the fourth class is full, which it usually is, then the only option is to sleep in the corridors, stairwells or on deck; if you plan to travel in this class, it's a good idea to buy a rattan mat before boarding to sit/lie on, and get to the port early to stake out your spot on the floor. Lock luggage shut and chain it to something immovable. Fourth-class food is edible at best, so stock up in advance with instant noodles and biscuits. It's always possible to upgrade after boarding, if space is available.

Where Pelni don't venture, you'll find that Perentis (Pioneer) freighters do, along with numerous local craft. While these are always willing to rent deck space to passengers for next to nothing - say US$1 for 24 hours - comfort and privacy aboard will be nonexistent. Bring your own sleeping mat, drinking water and snacks, though you may be able to buy rice and fish heads on board. Guard your gear and don't flash anything around. Schedules for these services are posted at ports.