Consider a J-shaped tube, open on both ends. After you add some water to the taller end, the bottom loop fills up. When you add more water, what happens? The water flows downwards even though the cell underneath is full.

That makes sense. The counterintuitive part for me was a cell causing the one underneath to become pressurized and then flowing back up. You don’t usually think of water as compressible.

A falling stream generates outward flow without piling up.

Watch your faucet run into a partially full sink: there’s a small depression where the stream impacts it — while the pressurized region under the stream pushes the water out and away.

This is in contrast to honey, which will form a mound when a stream hits, because of its higher viscosity.