By the way, having an idle few moments, I looked up the energy needed to compress air to the pressure 600ft down in the ocean. It is about 330J/litre.
You can get it from the 2nd graph at this site:
Horsepower required to Compress Air.
Where you can read off ~5.5W compressor power to compress to 17bar (which is the pressure at 600ft depth), at a rate of 1litre free air/minute. So for a rate of 1litre/sec you need 60x as much i.e. 330 Joules/second to compress 1litre/second to that pressure. So you need 330J for each litre of free air compressed.
However to produce a litre of air at 17bar, you need 17x as much free air, so you need 330x17 = 5,100J per litre of 17bar air, delivered at 600ft down in the sea.
Now, turning to these "buckets" on the conveyor, each litre of air introduced at the bottom displaces a litre of water, weighing ~10N, and so that is the buoyancy force it creates. As the conveyor rises, this does F x d work. Taking 600ft as 180metres, the work done will be 10 x 180 =1800J, again per litre of 17bar compressed air.
In summary, for every litre of compressed air you expend 5,100J to compress it and you only get back 1800J, 35% of the energy input. So, as a supposed source of "free energy", this device is spectacularly crap.
As most of us knew anyway, but still it's good to do the analysis.