by ftl_ftw
This is one case where the physical components provide the answer. The line has to be thick enough to be visible and thin enough to be drawn by a physical pen. There's no such thing as an infinitely thin pen. It also has to be drawn on the actual board as the board is, with the components/borders having an an actual size.As far as I can tell from staring at my own board, there simply no space to draw a sea lane that starts in Istanbul, north of the existing sea lane, and gets past Greece - there isn't even any blue-sea-colored space, it goes straight from yellow land to dark blue sea lane.