The tide changes approximately every six hours. I say approximately, because if it was exactly six hours, high tide and low tide would be at the same time every day. But they are not. The changing tide is impacted by the position of the sun, the moon, the earthâ€™s rotation, and the shape of the sea floor. You can read more about this on Wikipediaâ€™s tide article if you want.
Here in Dar es Salaam, the timing of the tide changes by 45 min (Â± 15 min) daily, and height of a high tide can differ by a meter. Thankfully modern science enables the production of tide charts (specific to location); I reference them daily here as at low tide I can walk through the tide pools exactly where I swim during high tide as the sea floor does not drop off at any great rate. Last night this meant that I swam as the sun was low in the sky and I watched the final bit of the sunset as I dried off on the beach. I also saw a jellyfish an armâ€™s length away, but that is a story for another day.