Helmet: Headdress of the Tides. From The Underbog.
Shoulders: Mantle of the Sea Wolf. from Mana-Tombs.
Chest: Harness of the Deep Currents. Shadow Labyrinth.
Gloves: Fathomheart Gauntlets. The Steamvault
Belt: Girdle of the Blasted Reaches. Hellfire Ramparts
Pants: Steadfast Legplates. Green item, search AH for it.
Boots: Steadfast Stompers. Green item, search AH for it.
Tabard: none.
Weapon: Melmorta’s Twilight Longbow. From The Black Morass. Quite easy to get, even though you might have to farm it a bit. It’s a replica for the legendary weapon from Tempest Keep.
The whole set drops from The Burning Crusade dungeons. The pieces of gear that might be the hardest to get are the green ones if you play on a low populated realm and the Auction House is not very active.