Along these lines, there's a good comic running right now called "The Last Mermaid".
It's set in a post apocalyptic world that's baked and turned into a desert. The last mermaid survives in a mech suit filled with water and her pet axolotl.
For some reason this post was posted 3 times by the scheduler so I removed the other 2 duplicates and let this be the one that remains since it has comments already.