In Civ5, playing on an archipelago map is like playing 1-2 difficulties lower than on a normal map. Firaxis never managed to make the AI understand how to launch naval invasions, or even how to defend against them. Do you think they will fix it for Civ6? (Obviously, I'm asking for pure speculation - we don't know it...) TBH, I don't have high hopes that they will. We already see from America's agenda that they think in terms of "continents" - which doesn't really work for archipelago maps. One thing they could do would be to treat smaller landmasses as a part of the nearest continent - and in the absence of a continent, to group archipelagos together and treat them as one. Other than that - I don't know.