A high or low tide occurs based on where the highest or lowest part of the wave hits the shore. A high tide reaches further up on the shore than a low tide. Most coastal regions experience two high tides and two low tides every 24 hours and 50 minutes.
Tides follow the pattern of the lunar day. The Earth experiences two lunar "bulges" daily that cause the high and low tides. High tides happen 12 hours and 25 minutes apart. It takes six hours and 12.5 minutes for the body of water to transition from low to high or high to low.
The moon's gravitational force is responsible for high and low tides. The moon pulls the water toward it in a straight line, resulting in a low or high tide. A high tide occurs on the side of the Earth facing the moon because it is closer. Low tides occur on the opposite side of the Earth because it is being pulled toward the moon. Inertia works to keep the tides from moving too much toward the moon. Hence, the tides are created because of the interaction between gravity and inertia when the moon is positioned in certain locations around the Earth.