Saltwater Power and Desalination Plant

Any high school science teacher is familiar with a saltwater battery science project. Two different types of metal in a saline electrolyte and what do you get... electricity. Oh, and of course ah... saline metal hydride sludge and chlorine gas. The gas can be harvested and sold for commercial use. The sludge, depending on the type of metal used can undergo further chemical reactions (possibly generating more electricity) to be turned into other commercially viable chemicals and drinking water. Since we have a nearly limitless supply of salt water (ok they said that about oil and coal and trees and ...) in the ocean plop a few thousand of these plants along the coastline. TaDa! Cheap electricity and water supply for generations to come... but not the generations after that.