In the south-west (north-west of Vivec) there is an island shaped like a viking helmet. If you swim behind the partially sunken ship, there's a small island directly S/E of the one I'm referring to, that has a water-logged crypt and a fishing spot. Anyhow, I noticed there were structures, a dock, and lighting (lamps/fire) on the viking helmet shaped island, suggesting it might be something that can be visited? Can't swim there as far as I can tell. Is there a quest that takes you there? Or maybe this will be part of a holiday event?