Historical and recent data reveal a very energetic regime on the shelf off southeast Florida. In addition to spin off eddies, large-amplitude tidal velocity fluctuations with amplitudes exceeding 0.5 ms-1 are observed. Recent exploratory measurements conducted as a part of the South Florida Ocean Measurement Center (SFOMC) show that the time scale of these oscillations is about 10 hrs. This period does not coincide either with the inertial period (27 Hrs) or with the semidiurnal M2 (12.42 hrs) or S2 (12 hrs) tidal constituents. In addition, these internal oscillations appear to be modulated seasonally. A possible explanation is that these oscillations are near-resonant internal seiches generated by barotropic tidal wave in the channel between Florida and Bahamas.