You can build fluid-based logic gates[1], so I think it should be possible to make a Turing machine (with the usual caveat that you'll most likely need such a large grid that actually simulating it is impractical)
Oh fluidics. Darn. I was hoping for some Boolean logic encoded directly in Navier-Stokes or something, e.g. some bath of water that had Turing complete flow patterns in some way. Though I guess that would actuallly solve the Millennium Prize problem...
