Knowledge of the times, heights, and the flow of tides is of importance in a wide range of situations such as navigation through coastal waterways; construction of bridges, docks, breakwaters, and deep-water channels; and for fishing, boating, surfing, and water sports.
![A graphic showing the frequency of tides and the tidal bulge of water due to the moon's gravitational pull. As the moon's position changes, the two tidal bulges rotate around the Earth. These bulges represent high tides, while the corresponding flatter sides indicate low tides.. (Image credit: NOAA National Ocean Service) A graphic showing the frequency of tides and the tidal bulge of water due to the moon's gravitational pull. As the moon's position changes, the two tidal bulges rotate around the Earth. These bulges represent high tides, while the corresponding flatter sides indicate low tides..](/sites/default/files/styles/landscape_width_1275/public/legacy/image/2019/Jun/tidefrequency_19x9.jpg?h=8f8b7512&itok=y52eyFpL)
Most coastal areas experience two low tides and two high tides every lunar day, or 24 hours and 50 minutes. (Image credit: NOAA National Ocean Service)