The Lord of the Rings: Sea of Longing or The Sundering Seas .
There is a popular YA fantasy book titled Sea of Shadows by Kelley Armstrong. If you were searching for that specifically, it isn't related to Tolkien's universe, though the titles are very similar! A Shadow of the PastThe Lord of the Rings : Sea...
It features prominently in the video game Middle-earth: Shadow of Mordor , making it a popular choice for fan projects or new stories set in that era. 2. The Sea of Rhûn (The East) The Lord of the Rings: Sea of Longing or The Sundering Seas