Stewart,
I'm such a dedicated rail/marine freak that I'm building not one but two layouts with a rail/marine theme. One, a 9'3" by 9'7" by 2' shelf layout, is a free-lanced version of Shelton. Wa that receives cars via carbarge. The sole major industry is a plywood mill, and there will be a few smaller industries like a batch plant, propane dealer and other small service industries.
The "big" layout will be 10' by 12' by 2' around the walls with a 2' by 6' peninsula, and will represent my CW Rwy's operations in Seattle, Wa. It draws major inspiration from the Milwaukee Road's Seattle operations in the late 70's, and is called the Duwamish Terminal It will feature carbarge operations to Shelton and Pt Townsend, the eastern terminus of the CW's isolated Olympic Penninsula branch. It will also feature some rail/marine industries and a variety of other larger industries.
Of course the two layouts will interchange cars via the carbarges.
Tom