We model the longshore dispersion of a passive, conservative pollutant in the surf zone formed by two-dimensional, monochromatic water waves of near-normal incidence breaking over a plane, flat, impermeable beach under presumedly uniform temporal, vertical, and longshore conditions. Such pollutants disperse in a Fickian manner through a plane moving at the areal averaged longshore current speed when the shore-normal concentration variation is small, with a longshore dispersivity reflecting diffusive and advective transport processes. We adopt an existing estimate of the turbulent diffusion and modify an existing longshore current model to derive a theoretical estimate of the longshore dispersivity; we calibrate the simple model with field data, generating accurate and physically plausible results.