<p>Unlike a fluid, the pressure at the base of a granular silo does not increase indefinitely with filling height. Instead, frictional interactions between the grains and the confining walls cause the pressure to saturate, a phenomenon known as the Janssen effect. Here, we investigate whether a similar stress-screening mechanism can arise when the confining boundary is not rigid but consists of a soft, self-assembled interface. The system studied is an underwater granular column of hydrophobic Magic Sand. When poured into water, the grains spontaneously form a thin confining layer, referred to as a granular skin, that encloses a dry core of grains and trapped air. By measuring the stress at the base of submerged sand columns of varying height, we observe a clear Janssen-like pressure saturation. Comparison with a conventional dry granular column shows that the granular skin supports a significant fraction of the applied load, leading to an enhanced stress screening. Synchrotron X-ray tomography reveals that this load-bearing capacity originates from the pinning of air–water interfaces to the hydrophobic grain surfaces, which stabilizes the confining skin. These results demonstrate that the pinned liquid-interfaces can act as effective load-bearing boundaries and play a central role in the mechanical stability of submerged granular structures.</p>