Washington state ferries will have Wi-Fi by summer: It's been a while coming, but a small firm in picturesque Port Townsend ran their first full-scale test between that town and nearby Keystone, one of the shorter ferry runs. The system uses 5 GHz (possibly 802.11a) signals from ship to shore, and 802.11a/b/g on board.
By summer, two heavy commuter runs for Bainbridge Island and Kingston will have the service in addition to the Keystone/PT route; by fall, the third heaviest single run, Seattle to Bremerton, will be added. The article lists the actual ferries that will be equipped. Even as a local, I'm not sure how many ferries run or in what rotation on each route, but it appears to be about all of the regular ships.
Nearly half of the ferry systems' 5.1 million passengers handled in the first quarter of 2004--remember, this is one of the largest ferry systems in the world, and the largest by vehicle volume--are served by the first three lines that will be equipped. Another 10 percent more will be added with the fall run.
The first three runs have crossings of about 30 minutes; the Bremerton run is about 60 minutes. Service will be free until fall, when a price for service will be set.