Desalination is a smart idea but has some down sides it costs 51 cents per cubic meter which is a lot but when you have a city of 1 million+ its going to add up fast. Another down side is two thirds of the water that's pumped out of the ocean can't be used that leaves one third left to use
which will be a lot more time consuming than using all of the saltwater.It also leaves a humongous environmental footprint but their using waves to harness energy to make the process greener in Galveston,Texas.