Steamboat

The Steamboat is a confirmed mode of transportation in Red Dead Redemption. (Steamboats actually do not appear in the game at all, oddly enough for them being a confirmed mode of transportation)

Steamboat docks can be found on gameplay maps. Since John Marston cannot swim, steamboats are used to cross large bodies of water. Steamboats are less common in the south, since the water is generally not deep enough for a steamboat to traverse.

At the southern shore of the Great Plains region in the West Elizabeth territory, there is an old abandoned port known was the Wreck of the Serendipity. The port has been abandoned because the large steamboat, The Serendipity, has partially sunk and settled on the shallow bed of Flat Iron Lake.

Trivia

 * John Marston is seen entering the west via a large Steamboat, mirroring the introduction of Niko Bellic on the freighter Platypus in Grand Theft Auto IV; another product from Rockstar Games.
 * Robert Fulton invented the first Steamboat.