If an appropriate logistic mod is enabled (Cargo Ships, Beautiful Bridge Railway, etc.) then "Super Searious Mode" can be enabled in the mod properties. Each island is surrounded by a relatively small ring of shallow water, and landfill can only be placed on shallow water. In order to actually connect islands one of the advanced logistic methods must be used.

I'm having trouble getting this mod to work. Do you have any tips. It's downloaded and enabled, but it doesn't show up as a scenario or in the mod or map settings.