"Till your land as they do along the Nile, Daughter Tarshish, for you no longer have a harbor. The Lord has stretched out his hand over the sea and made its kingdoms tremble. He has given an order concerning Phoenicia that her fortresses be destroyed. He said, 'No more of your reveling Virgin Daughter Sidon, now crushed! Up, cross over to Cyprus; even there you will find no rest.'" NIV translation
This judgment has far reaching consequences as all of the city states of the Phoenicians depended on Tyre and its harbor. They would be forced to return to farming instead of selling their goods around the world. It is once again made clear that the sea is not a god but the one true God is the one that has brought this about.
This judgment has to do with the island of Tyre as it was highly fortified but was conquered by Alexander the Great. He built a causeway and connected the island to the mainland so that he could get his battering rams to the walls.
"Look at the land of the Babylonians, this people that is now of no account! The Assyrians have made it a place for desert creatures; they raised up their siege towers, they stripped its fortresses bare and turned it into a ruin." NIV translation
The Assyrians under Sennacherib defeated the Babylonians in the year 689 BCE. Babylon was laid waste at that time and the destruction of Tyre is compared to it.
We must remember that Isaiah prophesied all of this before the fall. At the time of the destruction of Tyre, they would have been able to look back on what had happened to Babylon.
"Wail, you ships of Tarshish; your fortress is destroyed!" NIV translation
All of the city states that had depended on the Phoenicians would have mourned at its destruction. This same type of thing is described in the last days as the people mourn the destruction of the new Babylon commercial system (see Revelation 18). This will be a system of trade that excludes God's people and the system and its city will be destroyed just like Tyre.