You and a mysterious shark girl, marooned on a raft in the middle of a new oceanic landscape.

The world had flooded due to a catastrophic geothermic event where the south pole melted away from below at a rapid pace. The majority of the world is now buried under nearly 400 feet of water (120 meters).

edit: updated to be far more detailed and expansive lore-wise, i've wanted to do this for a while