Aquallor
This aquatic province of Arborea borders on Oceanus. The border is easier for the deep-dwellers to discern, as the sea floor slopes steeply upward to Aquallor's shallows. But sailors who are not careful can easily run aground.
Geography
The shallows of Aquallor are only around 3-5 feet deep, but "shallows" is still misleading. The province is streaked with massive deep-sea trenches, some of which stretch down even further than some of the chasms in Oceanus.
In the deeper areas closer to the Oceanus border, there are a few islands. These islands are not tethered to the sea floor, but float freely.
Localized Phenomena
Aquallor is a land caught in eternal summer. The islands and shallows are perpetually warm and temperate, and even the deeper chasms hold several miles of refreshing coolness before they become dangerously chill.