Question

Why are the levels of all the seas equal in the world

Answer 1

There is uneven land on Earth. So, the height of buildings,mountains ,etc. are measured from a fixed height that is sea level

Answer 2

Answer:

the height of land is commonly measured from the sea level and all the seas present in the world is connected to each other or in some way or the other .There is no sea left without connecting any other sea.So it is roughly taken as the same.