I would be interested to know the growth rate of the plants. Sunlight diffuses quickly under water, even just a few meters down. Will be interesting to see the economic feasibility of a large scale operation.

Hard to believe it could be profitable or scale as compared to other farming methods. Farming on the surface in a similar way might be able to do the same thing, with a feeder tube pulling cold water from deep below - which takes no power. It would be more accessible, less costly, but not as beautiful as these underwater gardens.