Alternatively, you might be referencing the "sea-longing" that many characters (like Legolas) feel as the Third Age ends.
Are you writing a about Mordor, or were you looking for a specific chapter or game level ? LotR Reread: The Shadow of the Past - Stewartry A Shadow of the PastThe Lord of the Rings : Sea...
The second part of your draft, "The Lord of the Rings: Sea...", could refer to a few different things in Middle-earth: 1. The Sea of Núrnen (Mordor) "The Lord of the Rings: Sea..."
If you're writing about a dark or "shadowy" location, this is a top candidate. It's a bitter, inland sea in southern Mordor where Sauron kept slaves to farm crops for his armies. A Shadow of the PastThe Lord of the Rings : Sea...