A small volume (117 cu-inch) seismic source producing signal predominantly in the 150-200 Hz frequency window was used during the GO calibration experiment in the Gulf of Cadiz (April-May 2007). The data show the small scale (< 10 m in the z direction) internal structure of the ocean. High-resolution images display seismic reflectors that often appear as distinct, horizontal, short (similar to a few hundred meters to a few km long) segments, lying at different depths, while low-resolution (similar to 20 to 30 Hz) display long, horizontal reflectors (similar to a few tens of km), sometimes linked by short, apparently "dipping" segments. The present data suggest that this apparent dipping effect is due to the insufficient separation power (similar to lambda/4) of the low resolution data. Improving high resolution acquisition systems hence appears to be a critical challenge to understand the seismic response of the ocean. Citation: Geli, L., E. Cosquer, R. W. Hobbs, D. Klaeschen, C. Papenberg, Y. Thomas, C. Menesguen, and B. L. Hua (2009), High resolution seismic imaging of the ocean structure using a small volume airgun source array in the Gulf of Cadiz, Geophys. Res. Lett., 36, L00D09, doi:10.1029/2009GL040820.