It is interesting that this has not been regulated but the FAA.
The Nov 1991 "Rotorcraft Night Vision Goggle Evaluation" paper that Hawley, Anoll and Green had prepared for the FAA before the implementation of NVG's in the civilian sector did not have much to say about the use of NVG's in off-shore operations, other than they considered off-shore to be an "extremely difficult operating environment".
They did, however, "recommended that the FAA investigate offshore use of NVG's as part of their continuing efforts".
Here is the link to this ancient, but interesting read:
http://www.dtic.mil/cgi-bin/GetTRDoc...c=GetTRDoc.pdf
I suspect the FAA had no interest in evaluating the use of NVG's off-shore, and so they just dropped the ball right there...
I have been researching this for months, but I have been unable to find any tangible performance criteria that has been published regarding the use of NVG's off-shore.
Most training criteria that I have been able to get my hands on, is either silent on the issue of overwater use, or merely states that water is "not a high contrast" surface.
I know that military and SAR have been going out there for years under these conditions, but I have not come across any of their findings....perhaps they do not wish to share?