You'll be fine.
All my flying is done over the ocean and I've flown thousands of miles.
What you're planning has no more risk than flying in an open playing field.
I would have no hesitation whatsoever in doing what you describe. I'd also be comfortable flying six feet above the lake en route to the location from which you want to shoot the photo.
Just don't rely solely on the altitude indicated on the...
Strange that in all the years I've been hearing this sort of nonsense, I can't find any recorded flight data to support it.
But I've found plenty that indicates the "plausible explanations" that you've listed above.