An instrument package has been developed that drifts along freely with the water while it repeatedly profiles ocean temperature. Profiling during drifting reduces the Doppler and fine structure effects that usually contaminate internal wave measurements. Six days of exceptionally clean internal wave records were acquired 470 km offshore of San Diego, California, in June 1973 at a nominal depth of 800 m. The resulting vertical displacement spectra decrease generally as ω-2 up to the local Brunt-V¿is¿l¿ (B-V) frequency. Just below the B-V frequency there is a spectral peak. Above the B-V frequency the spectra drop sharply to low levels. Vertical coherence of internal waves over a separation of 100 m was found to be 0.8 and fairly independent of frequency up to the B-V frequency. An internal wave model proposed by Garrett and Munk is in general agreement with the observed features. Both the measured coherence and the oscillatory nature of the spectrum near the B-V cutoff are consistent with an energy concentration in the lower six or so modes. In addition to the internal wave records, continual changes in the thermal structure were observed by the drifting package. One repeating thermal inversion pattern occurred four times during the 6-day thermal structure record.