This isn't really totally accurate. A lot of the water in the world is process water, it's created when things combust.

And much of the water consumed by plants is turned into carbohydrates which then gets processed back into water after combusting or being oxidized in a animal.

I actually highly doubt that any water remains that has never been broken back into its constituent atoms and then combined with other atoms.

I suspect the true answer is actually 0% of the water remaining today has ever been in a dinosaur. (I.e the atoms might have been, but not the molecule as a molecule.)