Full Idea
If a person exhibits water-seeking behaviour, they also exhibit H2O-seeking behaviour, so there is no way the behaviour itself, without reference to a mental component, can constitute wanting water rather than H2O.
Gist of Idea
Wanting H2O only differs from wanting water in its mental component
Source
John Searle (The Rediscovery of the Mind [1992], Ch. 7.II.4)
Book Reference
Searle,John R.: 'The Rediscovery of the Mind' [MIT 1999], p.158
A Reaction
What about the behaviour of responding to the discovery that this stuff isn't actually H2O? Or the disposition to choose the real thing rather than ersatz water? An interesting comment, though.