The trick is to flow seawater past the still and take only, say, 1% of the water from each litre that flows past, which you can do with a still as opposed to a

The trick is to flow seawater past the still and take only, say, 1% of the water from each litre that flows past, which you can do with a still as opposed to a filter. It's a bit like slingshotting a space probe past venus. Technically to move Venus a bit closer to the sun, but not enough to make a difference.