Pupfish

Desert pools with sand underneath, and nowhere else worth checking. They are one of the few critters allowed to appear while you are standing there watching, so you can wait at an oasis instead of doing the usual walk away and come back routine. They also die to almost anything, including a stray swing of your own, so net one the moment you see it rather than after you clear the area.

The Pupfish Bowl is the only real use, and crafting it is a one way trip unless you shimmer the furniture back apart.