The Depthworld - An "Underdark" for the Shifting Seas

[Lord Sessadore]

Yes, my impressions too - enough to give DMs ideas, but not enough to limit them really. Good job!

 

[Dunamin]

Thirded (I think?). Good inspiration for adventure builders.

 

[CaBaNa]

I love the idea, gives room for creepy catacombs, large cities, and other only under the world ideas.

I think all three can coexist as an amoebas-indistinct-almost-together-almost-different place where the lines between which you're in are only discernible by the DM's eyes...

Great ideas all.