During early development, the survival of aquatic embryos depends on effective defense mechanisms in the absence of a mature immune system. In the Xenopus laevis embryo, the skin is covered by multiciliated cells (MCCs) that generate powerful fluid flows. In this study, we combined experimental and computational approaches to investigate the biophysical mechanisms underlying this protective function. This work, at the intersection of biophysics, fluid mechanics and developmental biology, revealed that the biological system does not aim for energy optimization or maximum efficiency, but rather prioritizes functional robustness. This ability to maintain reliable protection even under non-ideal conditions (e.g. following injury or developmental defects) represents a key principle for organism survival.