The concept of the seven seas has changed several times over the millennia. According to modern definitions, the North Atlantic, South Atlantic, North Pacific and South Pacific seas touch North America.
In the ocean............. Jellyfish can be found everywhere! From the Arctic ocean to the bottom of the Pacific ocean to some of the shores of all seas. Every sea and ocean contains a species of jellyfish.
Rome was (and still is) on the Mediterranean Sea. This is why the Roman Empire was centred on the Mediterranean. Rome conquered all the lands on the shores of this sea, which they called mare nostrum (our sea).