What would happen to the environment if we found a way to replace Coal and Gas/Oil energy with Saltwater and completely converted to it?

Our energy demands would grow ever more voracious, and eventually the oceans would be the little puddle the Aral Sea is becoming.

No more fish for dinner, lots more farmland, but no water to grow crops.

Well, I could go on and on, but it's not really based on any practical science that we know of.

Unfortunately that wouldn't work.  Coal and oil are sources of energy because they contain a lot of energy.  Water (salt or fresh) is in a low-energy state - the combustion happened already when the hydrogen bonded to the oxygen.  You can't get more energy out of breaking up water molecules than you put into it to start the reaction.

Saltwater -   Two Parts Hydrogen and one part Oxygen pulse some impurities.

Pass a strong electrical current through the water.  This will separate the Hydrogen and the Oxygen. Capture the Hydrogen and Oxygen in separate containers.

Design yourself an engine that runs on Hydrogen and there you go.

Oh Wait!   that has already been done.

What would happen to the Environment?  It would be CLEAN.

I don't see how that is possible.