Great Lakes:

They are Lakes! They are huge bodies of water! Bigger than a lot of
seas! Can be very tough in a bad weather! That doesn't make them
anything but a Lake.

They are not at sea level. They have no tides. The flow of water is
always in the same direction, The outlet is always the same. That is
because they are Lakes.

Why must they be classified as a Sea? They are Lakes. Lakes to be damn
proud of! They are superior Bodies of Water, with their own weather
systems. They have their own ship traveling commerce that is busier than
most seas in the world.
They are a wonder of nature as they are.
What have they to gain by being labelled a sea?

Ole Thom