A wonderful visualization of tide cycles at the Exploratorium in San Francisco.
Each acrylic slice is a hanging record of tide levels for one day, so you can easily pick out the peak of high tide and the valley of low tide. These peaks and valleys shift from day to day and month to month, as influenced by the moon's gravity (and, to a lesser extent, by the sun's gravity). So the timing of high and low tides reflects cycles in the motion of the moon and sun. The highest and lowest tides occur each month at the time of the new moon and the full moon.
The Exploratorium exhibit, titled "Tidal Ribbon," represents the tidal record for one year (2011), as measured at the NOAA tide station near the Golden Gate Bridge.
Photos by I. Peterson