The Maelstrom was born when the Well of Eternity imploded, sundering the Middle Jungles of Suramar underwater. It remains as a permanent scar of what happened 10,000 years ago during the War of the Ancients.
Maelstrom will be added to World of Warcraft in a future expansion. Few months ago, ex-Community Manager Katricia said that the developers were working on content for the Maelstrom.
Nazjatar, the home of the Naga, is ruled by Queen Azshara, who survived the sundering 10,000 years ago. Nazjatar is where the Well of Eternity existed.
The Art of World of Warcraft book that came with the Collector’s Edition, offers two concept art images showing Goblin Submarine turtles. One seems to be a war-submarine, the other one looks like a transport. The Isle of Kezan (Undermine) map, shown in the Collector’s Edition Behind the Scenes DVD, shows a transport-route from Undermine to Nazjatar. The screenshot of that map is to the right of this page. It is unknown if the transport will be a Goblin Submarine, as no details of Nazjatar and Isle of Kezan has been announced by Blizzard, except what has been released on Warcraft RPG: Lands of Mystery.
Read our interview with Richard A. Knaak where he confirms that his War of the Ancients Trilogy books reveal that the Old gods saved Azshara and the highborne from drowning during The Great Sundering and stroke a deal with Queen Azshara. The Old gods transmuted the highborne into the Naga.
Formerly Zin-Azshari, Nazjatar city is found in a trench beneath the Eye of the Maelstrom. Nearby areas of interest are Mak’aru—capital of the Makrura lobster-men, Gishan Caverns, Pillar Deep, the Boiling Terrace, the Rift, and the Drowned Reaches. Details may be found in Warcraft RPG: Lands of Mystery from page 70-74. Prospector Brann Bronzebeard used an enchanted helmet to dive into the Eye of the Maelstrom to explore the ancient city of the Naga.