In most Simutrans data files, a station tile has a 5×5 square catchment area. In pak128.Britain, it's 9×9. From such small differences one can generate a truly efficient passenger transport system.
In Simutrans, there are various ways of crossing the sea, though they basically boil down to bridges and tunnels.
In Simutrans, it's easy to build huge sprawling stations that don't work very well. There are some convenient optimisations that will help things flow rather better.
Every so often I get an enthusiasm for something, go hard at it for a bit, then drop it again. I'm on my third go round with Simutrans.