uesp:

Did You Know: The Maormer, or Sea Elves, live on the island-continent Pyandonea, south of the Summerset Isles? The Sea Elves have remained independent from both the Aldmeri Dominion and Cyrodiilic Empire thanks to  "The Veil of Mist", an impenetrable haze that completely covers the islands.

The only known Altmeri fleet to have entered the fog returned with but a single surviving ship, who reported kelp that trapped every ship but those of the Maormer, giant sea serpents, and what land there was to be massive plateaus covered in dense vegetation.