Stream Line (1976)

The film is a continuous, "real time" tracking shot of a stream bed. The length of the track was ten yards. The camera was suspended in a motorized carriage running on steel cables three feet above the water surface. The camera pointed vertically downwards recording the contours of the stream bed and the flow of water along its course. The sound of the water was recorded synchronously from the moving carriage.

Unfortunately the movie Stream Line is not yet available on HBO Max.