KingKev,
Immigrants need a ferry crossing to go over water (assuming that there isn't a bridge), but the terminals don't need to be staffed. For anyone else to use a ferry crossing, both terminals must be staffed. Watch the labor-seeker generated by each ferry terminal, to make sure that he goes by housing. If the terminals have labor access but not are not fully staffed, then raise the priority of Infrastructure in the Overseer of the Workers (or get more workers). For example, if there's a ferry crossing with a food farm connected to one terminal and an empty granary set to "accept" the food connected to the other terminal, and if all buildings are fully staffed, and if the food isn't set to "Stockpiling", then the farm should deliver food to the granary (or somewhere else).
By the way, I vaguely remember hearing about a mission (which might be Abu) where it's possible to place a ferry crossing in a place where it won't work. I haven't verified the problem (it's never happened to me), but if all else fails, try deleting the ferry and rebuilding it in a slightly different location. (Before trying anything like that, save the game in case something goes wrong.)
[This message has been edited by Brugle (edited 01-07-2003 @ 02:52 PM).]