People are affected by three forces: gravity, buoyancy and support. When people walk to the shore, the volume of boiling water discharged by people becomes smaller, the buoyancy becomes smaller, and the gravity remains unchanged. Therefore, with the increase of supporting force, people's pressure on the stone increases, and the pressure of the stone on people's soles also increases, which leads to an increase in pressure, so it feels more and more painful.

So the answer to this question is: when you walk to the shore, the volume of boiling water discharged by people becomes smaller. From F-float = ρ-liquid V-row, we can know that people's buoyancy decreases, people's pressure on pebbles increases, the supporting force of pebbles increases, and people's foot pressure increases, so they feel more and more pain.