The Ferry is a major link between Portland and Staunton Island during the Callaghan Bridge construction. Only certain vehicles can enter the yellow marker to the other island. Naturally, you can just drive over the Callaghan Bridge construction. Later on in the game, the ferry is threatened to be closed for more work on the underground road. However this never happens, until GTA III (which was set 3 years after these events). It is said that for GTA IV you can drive this ferry, unlike in LCS when you watched a long cutscene.