Full Idea
If there is identity between water and H2O, we have neither the asymmetry nor the irreflexivity that explanations require.
Clarification
Things can't explain each other, or explain themselves
Gist of Idea
Two things being identical (like water and H2O) is not an explanation
Source
Paul Audi (Clarification and Defense of Grounding [2012], 3.3)
Book Reference
'Metaphysical Grounding', ed/tr. Correia,F/Schnieder,B [CUP 2012], p.105
A Reaction
Once you realise it is H2O, you understand its deeper features, which will open up new explanations. He's right, though.