Water and Pain.
In the attempt to prove that water and pain are not reducible in the same way, I will adhere to the views of Kim, Kripke and Davidson. This is in order to show that although they may be arguing for different points, they share some ideas that will be presented as a unified line of thought in this particular question. They all seem to share my intuitions as to whether pain can be correlated with c-fibre firing in the same way that water is correlated with H2O; namely, we agree in that the relation is different in each case.
I will describe my point of view based on the views of these three authors because I need Kripke’s proof of the necessary truth of natural kinds, which is what Kim[1] uses in a different way to argue for multiple realizability as a proof for denying that pain is a scientific kind. As for Davidson, I will use his ideas of homonomic and heteronomic reductions to strengthen my point. All (or at least Kim and Davidson) agree in that psychology will not be a science. I like that point of view, however I will try to present it from my perspective.

[1] I take natural kinds as scientific kinds.