Lamplit Abyss

The Abyss, a new frontier. At first only a few people entered the abyss. Explorers, Spelunkers, Magi and the like. But then the grand flood started. Coastal towns were under the water in a few days. Mountains within a few weeks. Those who survived would either enter the Abyss, or stay on the endless sea. You have the same choice, and it is a permanent one. But just because you don't enter the abyss. Doesn't mean you are free from its danger.