Science

I suspect that a large percentage of people worked with sodium metal, or potassium metal have put sodium or potassium in water for the "bang." I plead guilty myself. (Sodium metal is lighter than water and floats on the surface of it while bursting into a bright yellow hydrogen/sodium flame.)

I take it as a kind of joke. To say that under any such conditions water is a "metal" is at best disingenuous, but I'm fully aware that in the journalist world, something like this is prone to be believed, nonsense or not.