There are actually people exploring this. I saw a documentary at one point about passive ocean pumps (using wave energy) transporting water from lower layers up

There are actually people exploring this. I saw a documentary at one point about passive ocean pumps (using wave energy) transporting water from lower layers upwards to increase plankton growth. It seems the company Atmocean is doing things like this and James Lovelock wrote a letter about it to Nature, I'm not sure if this is necessarily related to the docu I saw though.