But we've got enough Nuclear to last a few thousand years with modern tech...
We've now got no fresh water problem and no energy crisis. We can even synthesise hydrocarbon based fuels in surprisingly large quantities- instantly ridding us of the problems of hydrogen production, transport, storage and upgrading the huge numbers of existing cars.
We have the prototypes of tech that would get us to Mars in a month and the asteroid belt in probably another month.
We have EHD tech that's just a decent power supply away from having us flying about with no moving parts.
We can produce bio-compatible parts to replace a huge number of lost or damaged bodyparts.
We can grow plants- food, "recreational" plants, all sorts of things- without vast amounts of water or even soil.
Stopping the possibly-rising tides is, I'd imagine, a problem well within our capabilities as a race to solve.
To paraphrase Peter Griffin- "Why aren't we using this?"
@DT well, because they need more water on aircraft carriers. It means they can last longer. Plus it's useful all over the world and is literally a billion dollar idea.