Hi there. The energy used for hydrogen production can be recovered using the buoyancy force of the gas created at sufficient depth of water. Suppose we use electricity to split ocean water to produce hydrogen. Then the produced gas is captured into containers which are attached to a conveyer belt and the conveyer belt turns electricity generators. On the surface we can release oxygen and hydrogen can be packed / transported for further use and/or used to on site to produce even more electricity. What would be the required depth at which the process would be self-sufficient ? ( i.e Energy used in electrolysis is recovered by the buoyancy force applied to turn the generators. Below this theoretical depth we would start to produce energy which would be commericaly viable. How water pressure, solemnization etc would affect the process ? Is sea water or sweet water better for the purpose ? My very rough estimation points to 100m below sea level. For test installation such a conveyer belt might be attached to and old oil platform. The construction would not require any high tech solutions and might be relatively cheap. The device might be as well completely submerged with electricity being transferred ashore by cables or it could serve as a Sea Hydrogen Refuel Station. What about inland lake installations ? Please advice as to practical solutions and the required calculations.