Maraqua
Maraqua is the name given to two underwater kingdoms: one modern and one historic. In order to distinguish between the two cities, the historic city is referred to as Old Maraqua and the modern New Maraqua. Maraqua is not the only underwater settlement, but it is the only salt water one as of yet discovered.
Old Maraqua
The Destruction
Main Article: The Destruction of Maraqua
Was destroyed by a whirlpool on August 18, 2001, following a flash movie released the previous day (17th August 2001) in which the Pirate Captain Dread, a skeletal Kiko, sailed to Maraqua in a submarine known in fanlore as The Revenge. Here, he demanded his annual 'protection money' from the then King Koi, who refused to pay (giving reasons such as a 'poor Kelp Harvest'). From the tone of this conversation, it can be presumed that Captain Dread regularly came for this money. The whirlpool is believed to be the result of a curse from this Pirate. The whirlpool, said to be ten miles wide, lasted until the 31st May 2002, where is finally subsided to reveal the Ruins of Maraqua.
Attractions of the Original Maraqua
Maraqua once housed the Underwater Kitchen Quests, later relocated to Mystery Island, and was the sole supplier of Utility Fish, which are now all retired and very expensive. TNT stated once that they originally planned for Utility Fish to be used as NeoHome utilities. Maraqua also sold Aquatic PetPets (most of which were redesigned and are being sold on Mystery Island).
After the whirlpool ruined the city, the Ruins began to be populated again, first by a gigantic Sea Slug, then by a Mysterious Statue (believed to be of the Darkest Faerie), then by a Bubbling Pit (listing all the available Maraqua-coloured Neopets), then by an Underwater Fishing area. The discovery and open trade with New Maraqua has promoted people re-entering the ruins, and it remains to be seen whether more will be made of this area by TNT.
New Maraqua
After the whirlpool destroyed the original city, King Kelpbeard set about building a new, more splendid city, with a strong army to protect it from its enemies. However, information of this was learnt by an armada of pirates, who sort to conquer the nation. The new city has a very 'popular' resturant and it is very hard to get into. Kelp, as it's called, obtains you an avatar if you feed your pet enough to be bloated.
History
As part of the Curse of Maraqua plot, Maraqua was rebuilt with the intention of being stronger than its predecessor so as to withstand any future Pirate attacks. New Maraqua has a standing army lead by Swordmaster Talek, something Old Maraqua didn't appear to have. When Captain Scarblade learned that there were surviving Maraquans, he lead another attack (this time with an army of pirates). They were fought off, however, in the plot.
Maractite
The Curse of Maraqua plot introduced the mineral Maractite, capable of traveling effortlessly through water as though it was in air. Information provided in the CoM plot suggests that supplies of maractite are running thin. According to the Maractite Axe card (Of the Neopets TCG), maractite slowly decays when exposed to air.
Maraquan Architecture
Visually, Old Maraqua's structure was very different from New Maraqua's. Old Maraqua was built out of transparashield, and had the look of a futuristic ocean colony. The smooth, bubble-like windows seemed to imply that there was an atmosphere inside the buildings. New Maraqua has a very coral-like appearance and is made out of Maractite, and is open to the oceans.
Plot Replacements
In the Curse of Maraqua plot, several replacements were made to the characters from the original destruction movie. Captain Dread was replaced with Captain Scarblade, Captain Dread's unnamed sidekick Blumaroo was replaced with Benny the Blade, King Koi was replaced with King Kelpbeard, and The Revenge submarine with a boat of the same name.
The original destruction movie was removed after the Curse of Maraqua (the page it was found on now only redirects to the About Us page) due to these inconsistences.
Misc.
A hint that TNT were to write the Curse of Maraqua plot was given in the Year Six Advent Calendar (27th December 2004), where a Rebuild Maraqua poster was given out with an animation put to the tune of Feed the World with the words "Rebuild Maraqua - Let them know Neopia loves them!".