The baltic sea has been called a Scandinavin Mediterranean. Explain why that comparison seems logical?

Like the Mediterranean, the Baltic sea is almost completely surrounded by land. And like the Mediterranean, the Baltic Sea has traditionally been a very actively used sea route for trade between the surrounding Baltic and Scandinavian countries: at one point the so-called Hanseatic cities formed the busiest and most important trade network of the Middle Ages. Most of these cities were located near or around the Baltic Sea.