There is a water taxi in Seoul known as the “Han River Ferry”. While most would consider this more of a tourist ride rather than a form of public transportation, it could also be used as an expensive, albeit relaxing, alternative to taking the subway across the river. You can get the ferry on Yeoido Island and take it either round trip (for one hour) back to Yeoido or to one of the other four ferry piers (and vice versa): Yanghwa, Nanji, Ttukseom and Jamsil. The cost is roughly 16,000 for an adult and 8,000 for a child. It is available from 9 am until 7:30 pm, Tuesday through Sunday.
