Expeditionary teams and explorers throughout history have tried to brave this hostile region that seems to plague the entire planet's oceans, but they've all either traveled so far into the fog that they run out of food and starve to death or have been killed by the threats within the fog within seconds of entering. For this world, the existence of these sea-based gates is absolutely necessary, because more than three miles out at sea from any given landmass, the sea suddenly turns into an impenetrable wall of thick, choking fog where ghost ships, freak storms, and giant sea monsters threaten to destroy any vessel that strays too far from shore. It's a world in the early Age of Sail where a naval-based portal network that connects all the continents and major landmasses in the world has existed since ancient times. It's got one major defining facet to it that drives most of the plot and I want to make sure I've shored up the logic of how this facet has shaped society so that it stands up to close scrutiny. So I have this mid-to-low fantasy world (which in this case can be taken to mean that it is a setting where there are monsters and various types of supernatural creatures but they're at least slightly grounded in reality, magic exists but isn't very common except amongst those rare few who have been blessed by the gods, and most of human society still follows the same basic rules you'd expect it to at any given stage of cultural and technological development).

Naval armada bermuda triangle