We present an analysis of relative dispersion over the inner-shelf off the coast of South Padre Island during the Inner-Shelf Dispersion Experiment (ISDEX). Coincident Lagrangian observations of coastal circulation with surface drifters and dye tracer were collected to better understand small-scale physical processes controlling transport. Patches of rhodamine dye and clusters of surface drifters at scales of O(100 m) were deployed in a cross-shelf array between 2 and 12 km from the coast and tracked continuously over a period of up to 5 hours with airborne and in situ observations. The airborne remote sensing system includes a hyperspectral sensor to track the evolution of dye patches, and a lidar to measure directional wavenumber spectra of surface waves. Supporting in situ measurements include a CTD with a fluorometer to inform on the stratification and vertical extent of the dye patches and a real-time towed fluorometer for calibration of the dye concentration from hyperspectral imagery. Experiments were conducted over a wide range of conditions with surface wind speed between 3 and 10 m/s, and varying sea states. Cross-shelf density gradients due to freshwater runoff resulted in active submesoscale flows. The airborne data allow characterization of the dominant physical processes controlling the dispersion of passive tracers such as freshwater fronts and Langmuir circulation. Langmuir circulation was identified in dye concentration maps during all sampling days except during a restratifying period. The observed relative dispersion is anisotropic with eddy diffusivities O(1 m^2/s). Near-surface horizontal dispersion is largest along fronts and in conditions dominated by Langmuir circulation is generally larger in the cross-wind direction. Surface convergence at fronts resulted in strong vertical velocities of up to -66 m/day.