In North Carolina the change in water level is about four feet. Considering the lack of elevation at the coast, the tides make a significant difference on where the water is located. A change in tide occurs about every six hours, however, based on the lunar cycle the time advances each day. When the sun, earth, and moon are in line we have very high tides, spring tides. When they are at sharp angles to one another we don't have as much change, neap tides.
Tides are predictable.
You can obtain a tide table to let you predict the tide times on a given day. When high tide comes to our coast, salt water moves in through the barrier island inlets, through our sounds and up into our rivers. Spring tides move the water further up the rivers. Fresh water flows from the rivers and off the land out through the sounds and inlets as the tide recedes. The wind also acts to push water one way or another.