Similar: gravity power by dropping a weight into the ocean. No construction. Much higher density. Less damage to environment. Problem is only to put the displacement weight in gas to the bottom which could be chemical and could hold until you need it with an anchor. Gas compression problem handled with pulley up of weight at lower depths. Could produce power not only going down, but up too. Most population is near the sea. Also associate with wind farms in the sea. Has someone done the math on this one? My guess is yes. The math seems pretty straightforward. Still needs rare earth for the magnets but...linear generators?