Eco is simulating a Planet. WhiteTiger seems to wanna do that too. But unlike in Reality our Roads are able to cross Oceans and even Deep Oceans (whatever the difference). With the addition of boats we should consider that Roads cannt cross Ocean and / or Deep Ocean.
It could give the Server more character and realism to limit the construction over these Terrains further. Testing different rules concerning roads and Ocean seems fitting to the coming playtest cycles.