The Sea of Thieves is surrounded by a Devils Shroud. In the lore and the books, it is repeatedly told that islands appear, which are then swallowed up again days or hours later.
What if random islands appeared at the edge of the map. Islands without names that we don't know yet and don't appear on the map. The only clue would be that, strangely enough, we see an island on the edge and that's why we notice it. Alternatively, one could create a cone of light or something similar that would then draw attention to it.
The island remains visible for X ingame hours and contains a lot of loot that the Pirate Lord has hidden there or gold from the ancient civilisation. The loot changes depending on the islands Lore. During this time we can visit the island and loot it. A threatening sign on the island tells us when it will be swallowed by the Devils Shroud and that is the announcement to leave quickly before the ship can take too much damage.
