We present a numerical study of bulk-mediated effective surface diffusion at liquid surfaces where surface-active molecules adsorb and desorb on experimental time scales. Adsorbed molecules execute Levy walks on the interface, each step entailing desorption followed by bulk diffusion and readsorption elsewhere. Our results confirm the predicted anomalous scaling of surface displacement r at times before pal-tides are finally lost to the bulk. Moments grow as (r(q))similar to t(zeta(q)), where zeta(q)=q for q<1, zeta(q)=(q+1)/2 for q>1. We have also confirmed that the "speed" c which characterizes the q<1 behavior, r approximate to ct, is universally related to other observables : c=D/h where D and h are, respectively, the bulk diffusivity and the slope of the equilibrium adsorption isotherm.