Great Sea

The Great Sea is the largest ocean in Totania, bordering all land to the south of the planet.

Expanse

The Great Sea stretches across the entirety of Southern Totania. It borders the south of the two major continents of Elone and Udai, and entirely surrounds the third continent of Shafai. It has some large islands, including the World Cell and those off the coast of Shafai: Abehir, the Pudazath Borderland, the Serene Islet, Cousin Island, and the Faraway Enclave.
The Great Sea reaches into various areas of water, such as smaller seas, rivers, and bays. Some of these include the Bay of Wonder by Zephys, the Tamdian poisoned bay, the Great Dip, the Strait of Ildial.
No one knows how far it spreads. Expeditions south of Shafai have yielded no results, with some believing Vecna is hiding something to the South. If he is, there is another landmass within it. If not, then the entire Southern portion of the world is covered in the Great Sea.

Water Characteristics

Unlike the Northern Sea, which varies in temperature as it gets closer to Moroza, the Great Sea is mostly warm throughout. One could travel from the beaches of Stallbourne, to the western portion of the Abral Islands, to the Southern Coast of Shafai and find that the water was always warm.
Some say that if there is land south of Shafai, the water there is likely cold. As no proof of it exists, there is no certainty to this fact. It is merely an assumption based around the Northern Sea and Moroza, alongside the theoretical counterpart to Moroza.

Creation

Totania was formed in the forge of Moradin, crafted carefully by the God of Creation. However, he only made its shape and general landmass structure.
Melora, Goddess of Nature, populated the world with plants and animals. While this was good enough, they could not sustain themselves. So, she created various bodies of water, finishing up with the Great Sea.
She considered it to be necessary to sustain the planet. Water was an important resource, and to create a giant body of it was important for making it liveable for her animals, as well as the Dragons that Bahamut and Tiamat had made.
Sehanine, jealous of Melora, copied her and created the Northern Sea, destroying the Giant Kingdom in the process.

Gyre

The Great Sea has two major gyres, or tidal whirls. One below Elone/around Shafai and another below Udai.
The Shafaian Gyre rotates clockwise around Shafai, aimed right beside the Great Dip.
The Udaian Gyre rotates counter clockwise below Udai, leading away from the World Cell island and around the Key of Beasts.

History

The Great Sea has a deep history, though there are only some few major events that it took a starring role in.

Colmiceth Nurdesh by andreaspsillos4

Poison Peninsula

Colmiceth Nurdesh, the founder of the Draconian village of Tamd, found himself and his alchemists at war with the Bards of Ealla.
The Bards declared war with a poem, and so Colmiceth decided to outdo them both in poetics and in strategy. He and his alchemists created poisons and gathered at the peninsula, where Nurdesh exclaimed

"Now perish in my Poisonous Peninsula, you perfidious performers!"

— Colmiceth Nurdesh

They poured the poison onto the peninsula, making it impassable. This won them the war, but ultimately it would partially drain into the bay around their land. Over hundreds of years, this made the waters around Tamd just as impassable as the peninsula itself.

The Southern Nereid Kingdom

For some time, the Nereid Kingdom was one, and all the Nereid people were united in the Great Sea. However, the time came when a rebellion grew in the Northern Sea.
The Damolnath family of Nereid rose up and created their own kingdom, the Northern Nereid Kingdom, splitting from the Southern Nereid Kingdom that resided in the Great Sea. The Southern Nereids, then, grew more hateful to those outside of their sea, and became a kingdom focused on military and protecting their land from potential invaders.
Traveling in the Great Sea afterwards risks attacks from the Southern Nereid military, a deadly force that few have survived against. They often fight against the Draconian village of Bortan, an equally militaristic society on the southern coast of Elone, bordering the Great Sea.

Neized Shaka by Jarhed

Shafaian Expedition

Neized Shaka was a Human who was present for the Dreamless Sleep in Nerodil. However, unlike a majority of the Humans, Shaka led a group that opposed Gellark Lionrage's plans for settling down.
Shaka did not want to steal land from the Goblins, and so he led his people on a nomadic quest South. Ultimately, they gained boats from the Draconian village of Bortan and sailed into the Great Sea.
These three boats were called the Kasai, the Vaal, and the Benue.
The Southern Nereids sunk the Benue and put a hole in the Vaal, though it made it to Shafai before the hole sunk it. The Kasai reached Shafai with no damage, even saving Neized Shaka, who was on the sunken Benue.
This ultimately led to the settlement of the Shafaian people on the continent, where their city of Iganjojo was founded on the water in a bay that drained into the Great Sea.
The Great Sea keeps them isolated from much of the rest of the world, making travel either way dangerous.