Honestly, I don't see (sea?) it. Every advantage of space are found in oceans/seas, especially if we use dead zones where aquatic life is already dead. The cooling is cheaper, tide+wind+solar is cheaper than space solar (I know someone who worked on a lens to observe the sun, the satellite was launched but due to being cheap on the solar panels, the sunlight and radiation chipped away the coating that found itself attracted to the most massive object in the area, the lens). Anti-corrosion is cheaper than light radiation protection, and servicing is way easier and cheaper.