The world sinking into the sea is not all that crazy after seeing what happened to Lulushia and wondering for years why it is there's so much ocean and people are cut off from each other due to the Red Line. We've had post-apocalyptic vibes for a long time, yet there's still plans on sinking the entire world probably because it's the only way to stop all Devil Fruit users and ensures only Mary Geoise survives.
('Course, they're run by a bunch of spoiled brats who can't perform physical labor, so they're going to starve anyway lol.)
Though now I'm thinking that the World Government must've known about this, suggesting it's their plan all along, or this was naturally going to happen and so there's an actual time frame for when it'll happen and the end is nigh. But instead of saving the whole populace, they're going to just save themselves and go back to the Moon.
Damn you, Golden Week!