Washington state ferry system moves ahead with trial of Wi-Fi on board with one ship this month: The service should move onto three routes and six ferries by fall covering the most popular commuting routes to and from Seattle: Bremerton (ship yards), Bainbridge Island (bed room community), and Kingston (the Olympic Peninsula's launching pad).
The service is being installed by a firm in beautiful Port Townsend, a gem of a former boom town out on a tip of the Olympic Peninsula. The trial service will be on a ferry route that runs between PT (as it's called) and Keystone, a town on Whidbey Island.
The article says that Mobilisa is trying 802.11a and 802.11g to link back to the mainland. I assume that they will purchase tower rights with line of sight to the predictable, set ferry routes. Since the company and the service is in our vicinity, expect some first-hand reporting when the service rolls out.