Assuming you were successful… Where do you put it all? I don’t mean the plastic, but the water.
You now have an arbitrarily large quantity of plastic-free seawater. If you put it anywhere but the ocean it came from, you either have to replicate the living conditions of the fauna you were trying to save or you accept having to kill the fauna you were trying to rescue in the first place.
Putting it back isn’t an option either, as it will simply be contaminated by plastic in very short order.
Worse yet, even if you did this on a truly enormous scale – see 1.3Bn cubic kilometres of water – you’d end up not with areas that are plastic-free and others still contaminated, but with a somewhat diminished concentration in the oceans as a whole.
