Water and sound waves alone aren't too interesting, but when you combine the two, optical illusions happen. To try this experiment out for yourself, you'll need to: "Set up your camera and switch it to 24 fps. Run an audio cable from your computer to the speaker. Set your tone generating software to 24hz and hit play. Turn on the water. Now look through the camera and watch the magic begin. If you want the water to look like it's moving backward set the frequency to 23hz. If you want to look like it's moving forward in slow motion set it to 25hz. Continue reading for a video and more information.
According to YouTube user BrassPup: "The effect that you are seeing can't be seen with the naked eye. The effect only works through the camera. However, there is a version of the project you can do where the effect would be visible with the naked eye. For that project, you'd have to use a strobe light."