Many years before The Wind Waker begins, the land of Hyrule was flooded by the Gods as a last resort to stop Ganon's forces when the Hero of Time did not return to destroy them. Its surviving people fled to the mountaintops and tried to restore their peaceful lives. These mountaintops became the many islands of The Great Sea. Many years passed, and the people forgot about the history of "Old" Hyrule, except as a bedtime story told to children, and in a coming-of-age ceremony for young boys.
The Great Sea is "illusory", and its waters from the heavens are different from Hyrule's native waters. Because of this, only monsters and Fishmen are able to live in the Great Sea.[2][3] It is because of these ethereal waters that the Zora race had become the Rito.[4]
Governance
The majority of the islands in the Great Sea are actually uninhabited, meaning that no one governs them; neither Outset Island nor Windfall Island are governed officially, despite their dense population. Only Dragon Roost Island (with a Rito Chieftain and the Sky Spirit Valoo), Forest Haven (with the Great Deku Tree as the Earth Spirit), and Greatfish Isle (with Jabun as the Sea Spirit) are known to have guardian deities. In addition, certain islands are owned by individual characters for private purposes.
Economy
Like in most lands in the Zelda universe, and because of the fact that the Great Sea is born from Hyrule, Rupees are the means of currency, which is accepted in every inhabited island in the game. However, the economy is a bit more diverse than in the former land of Hyrule, given the different businesses run; for example, Traveling Merchants fuel trading sequences by selling their goods to travelers and also sending them to major shops and retails to give townspeople access to them. Auctions are run in Windfall Island every night, and Beedle's Shop Ship can be seen sailing around numerous islands as well.
The weaponry in the Great Sea is more advanced than it was in Hyrule before its flood. Navigating across the waters are Warships capable of shooting at enemies from long distances. It's unknown whether these boats are piloted manually or work automatically (in the latter case, it would indeed prove how much advancement is shown in regards to technology in the Great Sea). Mounted in coral reefs and high platforms are cannons that can shoot bombs to distant enemies, and operate on their own.
Advanced tools and devices can be found as well, such as the Tingle Tuner (which allows communication between the user and an assistant for various purposes), color-recording Picto Boxes (used to take pictographs that become important for figurine making), and pieces of ancient technology (as seen in Tower of the Gods and Wind Temple). Aside from this, it is unknown how much Hyrule had progressed in this aspect before being flooded, thus it is unknown how much was lost before the aforementioned divine intervention.
The Great Sea serves as the overworld of The Wind Waker. Most of the islands in the Great Sea are quite small, with little intelligent life inhabiting them. The chief island is Windfall, which houses various shops and attractions, and has the only major human village, except for a small settlement on Outset Island, another important location. Aside from these islands, some of the more prominent ones in the Great Sea include:
Dragon Roost Island, home of the Rito tribe, where the Great Sea's main messenger company is located.
Forest Haven, home of the Korok tribe, whose inhabitants are dedicated to traveling across the Great Sea to cultivate trees in order to create new forests.
Forsaken Fortress, former home of a clan of pirates, and source of the evil present throughout the events of The Wind Waker.
Greatfish Isle, formerly the home of numerous people and the Water Spirit Jabun, it is destroyed by Ganon at a point in the game.
Tower of the Gods, hidden fortress said to wait for a Hero to raise it from the Sea's depths.
There are many people in the Great Sea, but the main group is Hylian. They live on Windfall Island and Outset Island, but some are also scattered around the Sea. The Rito live on Dragon Roost Island with the Sky Spirit Valoo, and the Koroks reside on Forest Haven with the Great Deku Tree. Gorons in this game are in the form of Traveling Merchants. No signs of the Kokiri or the Zoras remain, as they gradually evolved into the aforementioned Korok and Rito, respectively. Also, a fish creature called Jabun, the aforementioned Water Spirit, is in this game, resembling Jabu-Jabu and the Fishmen (the latter inhabiting the waters of the Sea). Finally, there is at least one group of pirates, Tetra's Pirate Crew, along with other seafarers, such as the Salvage Corp.
Enemies
A number of enemies are encountered solely or primarily on the Great Sea itself instead of inhabiting its islands:
The following section is not part of the Zelda canon and should not be taken as such.
Super Smash Bros. Brawl
The Great Sea appears in the Pirate Ship Stage in Super Smash Bros. Brawl. The stage features a scale version of Tetra's Ship floating across various locations from the Great Sea. These include a Lookout Platform that shoots bombs at the players, a Cyclone that throws the ship into the sky, later descending back to the Sea, and a rocky island where the ship crashes, forcing the players to use the island as a new platform.
The King of Red Lions makes a cameo appearance floating behind the ship every once in a while, creating an extra platform.
Trivia
If Link decides to leave the Great Sea, the King of Red Lions prevents it by telling him that it is too dangerous and then turning around.[5]
↑When the Hero of Time was called to embark on another journey and left the land of Hyrule, he was separated from the elements that made him a hero. It is said that at that time, the Triforce of Courage was split into eight shards and hidden throughout the land. Even I do not know where they rest, but this much I do know: they lie hidden somewhere in this Great Sea. — King of Red Lions (The Wind Waker)
↑The Great Sea in The Wind Waker is an illusory ocean created by a torrential downpour from the heavens. Its ethereal "water" is unlike the water natural to Hyrule, and so only monsters and Fishmen are able to live there. (Encyclopedia, Dark Horse Books, pg. 65)
↑Oceans... Oceans... Oceans... Oceans as far as the eye can see. They are vast seas... None can swim across them... They yield no fish to catch... — Ganondorf (The Wind Waker)
↑The Zora, unable to live in the Great Sea's ethereal waters, evolved into the Rito, who are able to fly in the skies. (Encyclopedia, Dark Horse Books, pg. 69)