A while ago a player posted a screen shot of him standing on a barren Vvardenfell. He wouldn't say how or when he got there. I believe this was during beta, when slaughter fish were too busy spawning to notice him. I'm stilling working on how to get to Vvardenfell from Stonefalls, but I did figure out how to get to Vvardenfell from Bay Foyen. The first part of the video shows how I did it, and the end of the video contains a slideshow of what the coastline looks like if you could swim to it. I used screen shots because the original video was too long to post to Youtube, so I just included some of the main screenshots from the original video. I place comments on video too.
Originally, I used this secret door in Bal Foyen to see how much of Stonefalls was included in the Bal Foyen zone, and it never occurred to me that there may be a way to cross the Vivec Sea because the Vivec sea extends the east end of the Bay Foyen zone, but I noticed that on the west side of the Bay Foyen zone there was a stretch of coastline that at the time didn't interest me much.
Although you can actually crouch under water on the east part of the Bal Foyen zone, you get killed by slaughter fish as soon as you touch the surface of the water when reaching the Vvardenfell coastline.
The video is interesting because the first part of the video shows areas of Bay Foyen that most players will never see. Accessing this area isn't easy and you need to be a sorcerer with the streak ability to do what I did in the video. What makes Bay Foyen and Stonefalls unique is that both are surround by flat vertical cliffs around most of the playing zones making it extremely difficult to find a way to breach the zone's forbidden areas.
I sped up some of the video to make it fit within 6 minutes. The video is recorded at 1080p, so if you want to watch it at that resolution you will need to switch to Youtube and change the view options to 1080p.
Enjoy!