The Taima Ferry (臺馬輪) leaves Keelung six evenings a week and sails through the night for the Matsu Islands (馬祖列島), an ROC-controlled archipelago around 150km northwest of Taiwan.
There are various ticket options, the cheapest being nothing more than a padded seat in one of the lounges. Most people opt for a berth in one of the bunk-bed dorms; at NT$1050 per person one-way, it's almost half the price of flying from Taipei to Nangan. These bunks are fairly comfortable and you have a curtain you can draw across for some privacy. Unfortunately, all the lights are left on throughout the voyage, which takes eight to ten hours. There are also first- and business-class cabins, but from what I saw they aren't worth the extra money unless you've a great need to watch TV. In the lounge you can buy beer, tea and instant noodles.
It's worth staying outside for the first hour or so as you get good views of Keelung Harbour and its impressive freight-handling facilities [see above and below]. Also, the ocean is dotted with fishing boats using dazzling carbon-arc lamps to attract fish.
The vessel is quite substantial - the car deck can take more than a dozen small trucks - so even if the weather is poor, the pitching and rolling are tolerable.
I woke up around 5am and went outside. We passed several small islets; officially, the Taiwan-ruled portion of Lienchiang County consists of 19 islands, but that tally doesn't include several isolated rocks.
Matsu's docks depend on military personnel. Each time the Taima makes a stop [such as Nangan (南竿), pictured left], teams of soldiers tie the ship up. Note that the man closest to the water's edge is held by the fellow behind - a wise precaution, I'm sure.
At Nangan the Taima [bottom picture] paused for two hours, during which we hit the island's main market for some breakfast. Then we reboarded the ferry for the two-hour voyage to Dongyin (東引), where we spent the first night.