Now, there IS an underwater themed street, but it's based on a dry cave made of coral. The physics are normal for land, and the colors are dusty rose and orange.
-1. I don't think that's a good idea. If you want the underwater stuff but have trees and animals, things could go wrong. However, here's an alternate idea basically the same.
I want an underwater home street! It doesn't need to have the same swimming physics, in my opinion, but I would love to have a mermaid glitch swim around her home street. :D