Environmental policies and laws in Asian countries are entangled with widespread corruption at all levels of government, cronyism and money politics. The idea behind the devices is so simple. The buoys sit in the ocean. The natural turbulence of the water moves them up and down. Mechanical devices inside the buoys convert that motion into electricity, which travels ashore by way of wires attached to the bottom of the buoys.
Nothing is burned.
No greenhouse gases are emitted. No chemicals are produced. No noise is made. The buoys aren't even visible from land. You can read about it in New Scientist.