Because Leg 204 followed a high-resolution 3-D seismic reflection and ocean-bottom seismometer site survey, no additional underway geophysical data were acquired during the leg. We did, however, take advantage of the fact that we would be on the southern summit of Hydrate Ridge at Site 1249, where bubble plumes had previously been observed in the water column using 12-kHz echo sounding data (Fig. F3 in the "Leg 204 Summary"), to obtain additional 12-kHz data. The objective of this effort was to obtain a time series of changes in bubble-plume intensity over a period of several days. Recording capability, which was restricted to analog paper records displaying nonoverlapping depth scales spanning 750 m, was not ideal for this effort, but we hoped to obtain some qualitative data that would permit us to evaluate whether a more quantitative approach would be fruitful in the future. Data were very noisy because of ship noise, and no unequivocal evidence for bubbles was obtained.