You have a few facts slightly wrong, Professor.
As a Scientitian in the field of Waterology, I can tell you that the 5000 gallons of water that up the fresh water of our Earth’s oceans are constantly being recycled by the elephants that the Earth rests on. This water is being drawn out via the elephants trunk, and then sized to scrub the giant turtles shell that the elephants stand on. In a magical process known to scientitians as “osmosis” the water which is used to scrub the shell magically becomes clean, and is put back into the oceans by the elephants.
So while I agree that the Earth cannot he more than a few thousand years old, as water is constantly being reconciled it actually won’t run out until the elephants eventually die, which will most probably be some time till next Match.