Read this thread on marine protection and growing rock underwater.  https://twitter.com/TypeForVictory/status/1684852532726611968?s=20

'By passing an electric current through steel rebar underwater, dissolved minerals (calcium carbonate, magnesium, chloride, and hydroxyl ions) accrete around the cathode. Over time the chloride ion gets replaced by dissolved bicarbonate, hardening into hydromagnesite-aragonite-

With oxygen evolving through a porous structure. The resulting mixture is equivalent in strength to concrete, and it grows, strengthens, and self repairs so long as there's an electric current.

The process releases CO2 gas, but de-acidifies the water.'