UNDERWATERTALE:
Ruins/Home/New Home – Atlantis
Snowdin – Coral reef
Waterfall – Deep, dark sea bottom (Think the trench from the first SpongeBob movie)
Hotland – Sunken ships of pirates/sailors/vikings/etc.
The Lab/Core/True Labs – Underwater marine base-type place/setting
Ruins monsters – Sailors
Snowdin monsters – Pirates
Waterfall monsters – Mostly the same as normal (Fish-people), except Undyne’s a viking now
Hotland monsters – Vikings
Core monsters – More sailors
Amalgamates – All of the above

I respect this AU.

Mainly because you make Alphys even more adorable.