Humanity is on the verge of a water crisis.
Only the latest example is the state of California, where a multi-year drought is now threatening billions of dollars of agriculture, as well as residents' lifestyle.
There is no way to conserve out of this crisis -- Southern California has already drained several lakes, and its population continues to grow in a desert region that is incapable of providing the necessary water.
There has been talk of desalination plants, with the usual conclusion that they are too expensive to operate. This expense comes from the power needs to generate the 5500 - 6900 kPa (800 - 1000 psi) necessary to push the salt water through the reverse osmosis membranes.
Yet this pressure can also be generated by the ocean itself, at a depth of 555 - 695 m (1,820 - 2,275 ft).
There are several locations around the world which happen to have sufficiently deep oceans in close proximity to the coast, for instance Australia, Oman, Somalia, and even just off the coast of Los Angeles, California.
In fact, closer than Santa Catalina island, not even 35 km (22 miles) from Los Angeles, the ocean depth measures 938 m (3,077 ft).
By constructing a desalination plant at the bottom of the ocean, the extensive power needs to generate the reverse osmosis would be negated. This would of course be offset by the pumping needs to return the fresh water to the surface. Yet like a siphon, that pressure would only need to be applied to start the flow of the water. The result would be a pipeline of fresh water. The resultant brine effect, so often citing as a detriment of desalination, would be located at the ocean floor, many kilometers from coastal fishing operations.
Lastly, by providing the startup pump power with solar power, the result would be an entirely sustainable fresh water source. The initial cost increase in constructing such an advanced facility would easily be recaptured by the many years of essentially free fresh water.