but I guess water is replenishable, but in a sense, is it completly safe from running out completly? If there was something big enough to start eating away at it? Even if it lasted thousands of years?
no, because the water has no way of going out of the atmosphere, even if a giant monster drinks it all, because then, it will die, and the water will evaporate from him eventually and come back to earth
We just talked about it the other day in my chemistry class. Lol, we proposed some far fetched ideas about it though. I'm thinking use solar panels to harness the power of the sun, use that that to make steam, and propel the car. Also, the car would would use the sun-power to charge the battery during the day so you could still drive at night.