<p>Aquatic plants have significant effects on wave dynamics and contaminant transport. Using a laboratory canopy model, we investigated the interaction of a surface wave with flexible stems with a focus on the case when the wave frequency is close to the natural frequency of stems. The experiments were conducted at various wave frequencies, wave heights, and vegetation densities of 0.8% and 1.2%. The oscillation amplitude of the stems and the lateral dispersion coefficient were measured. Image processing techniques were employed to analyze the experimental data. The results indicate that the oscillation amplitude of the stems is larger than the orbital displacement of fluid particles when the surface wave frequency approaches the natural frequency of the stems. However, the intensified longitudinal oscillation of the stems does not lead to rapid cloud expansion beyond the effects of turbulence and vortex shedding, represented by the Reynolds and Keulegan-Carpenter numbers, respectively. The results confirm that denser vegetation results in a higher transverse dispersion coefficient. By comparing with the available results for dispersion coefficient under current, we found that the lateral dispersion under wave action is much smaller than that under current.</p>