Here is a simple composition from Ruby Beach that I created by placing the camera very close to the sand. Part of Ruby Beach is very shallow, and at low tide this allows you to experiment with some creative compositions.
Click on the image above to view it at a larger size. You will be able to see sharp rocks and bubbles in the foreground. They seem to be superimposed on the shifting water. This was accomplished in camera. I opened the shutter release just before the wave passed under the camera – capturing the impression of the rocks and bubbles. As the wave passed by, it created a secondary impression on the sensor, which remained open for a few moments longer.