The Sealands

The term "Sealands" refers to only part of this setting. The Greater and Lesser Hallic Seas, and the Aldean Ocean to the west, are full of islands of various sizes (from Indonesia-like on down). These are inhabited by various peoples and creatures, some of whom trade with each other and some of whom exist in relative isolation.
Since the Aldean Ocean either borders on The Feywild, or is partly on both sides of the borders, things get weirder as you go west, but even closer to the mainlands of Findere and Chadun, in general the Sealands are considered pretty chaotic territory.
The Hallic Seas are named for an ancient empire, now long defunct, that spanned many of the islands in the area (and parts of the mainland). Nowadays even the location of the Hallic capital (Hallam) is uncertain. More recently, the closest thing to large polities have been warlord states competing with each other. Until about a century ago, these warlords were referred to collectively as the Sea Kings (or Pirate Kings by disapproving observers).
Vacena, ten day's sail south of Malfa, is the largest city in the Sealands and generally considered its southern end. The Vaceni navy is famously the best in the world, but they rarely have much to do with the Sealands, being focussed southwards.