Interesting question! I study things like volcanic activity and mountain building processes, so I was at a bit of a loss when I read your question. Working with other scientists is really important in geology, so I asked my friend who is an expert on lagoons and coastal geology. Here is what he had to say: Tides are a result of the gravitational attraction between the earth, the moon, the sun, and the water that covers the earth. When the moon and sun are aligned, the difference between low-tide and high tide is the greatest. These are called spring tides. Depending upon the location on earth, these gravitational forces cause some beaches to have semi-diurnal tides, and others to have diurnal tides. For a semi- diurnal tides there are two high tides and two low tides per day. A diurnal tide has one high tide and low tide each day. Some locations on earth such as the Bay of Fundy have tide ranges of 53 feet! Using the tides for energy production is a potential source of green energy.

There are ways that you can set up the currents that are caused by the inflow and outflow of the tide to cause a beach to seem like it has more than two tides. I don't know enough geometry of tides to explain this.