1. Moving sources up/down in a borehole. 2. Depth oscillation of a logging sonde because of unequal drag as it is pulled up the hole. 3. A method of marine seismic shooting in which the seismic cable or streamer being towed by the recording boat is alternately released so that it floats freely in the water during recordings, and then is reeled in between recordings to catch up with the recording boat, which is traveling steadily ahead all the while.