Velvet. You are most correct about the gap in FAA regulation on this. But trust me when I say, and as others have said, if you are flying single pilot in a bird that is anything less than 4 axis over night to an unlighted area over the ocean, goggles or not, man I hope it is important because you are playing with fire.
When it comes to the regs, overwater FAR's talk about having floats on helos
However, look at this way( hypothetical): the weather forecast says 6 miles in haze and overcast layers at 2K, 5K, and 10K. No wind and the moon isn't up for 3 more hours. After 5 minutes pointed at 90 degrees outbound to whatever coastline you are flying from it is freaking dark. Goggles will have nothing to enhance and it is an instrument game from there on out. Visit the US Naval Observatory and hit "data services" then select sun and moon data for the day. PM me if you have questions.
The FAA DOES say that if you don't have a visual surface reference, or at night, a visual surface light reference to safely control the helo...you are in the wrong, and you aren't allowed to operate IFR outside controlled airspace below 1200' above the surface (unless your operation has been looked at by the administrator for exception).
I have made a career flying over the water in two maritime, military services, and we aren't keeping any secrets about the issue. There are plenty of fatal accidents on file (non-combat related) where spatial disorientation claimed the lives of fine aviators in the sexiest of machines.
If you have no visible horizon, goggles or not, then you need something to orient, like an attitude indicator, and there you are... ON INSTRUMENTS. Best lesson I can pass on to you is: don't look at the regs to justify your overwater operations, they will be found lacking. It sounds like you have already seen some dark events, now use that hindsight and recall if you had a horizon...if you didn't, then you probably got lucky (regardless if the regs don't prohibit you from doing it)
Official sunset to sunrise over any significant body of water...play it as if you were IMC. If you are not instrument rated...the risk is not worth the gain.