Years ago, I had a conversation with a zoologist during which he stated that “we don’t need to worry about food, we can feed ourselves from the ocean”.
I asked how, he said “ocean farming”.
At which point, I pointed out that nobody “owns” the ocean so establishing farms anywhere but just offshore is difficult to impossible, a relative paucity of “police” to prevent rustling and the fact that you can’t fertilize the ocean because the currents take it away to somewhere else.
He dismissed all this, and we parted on bad terms.
Those issues still haven’t been solved.