THABO Mahlatsi would like to know more about the term "sea level".
Sea level, or mean sea level (MSL), is a measure of the average height of the ocean's surface - the halfway point between the mean high tide and the mean low tide.
It is used to calculate heights or depths on the surface of the earth.
For example, Mount Everest is considered to be 8 848m above sea level. - isegeek.com; wikipedia.org