Question

How are the size and shape of oceans continuously changing

Answer 1

Sea floor spreading. In the middle of the ocean there is the mid-ocean reef were magma comes up from the mantel and cools this is also why the continents move. There is also erosion.

Answer 2

Sea level rises when it rains or when snow is melting. Sometimes more water forms in new areas and makes it into an add on to the ocean which Changes the shape.