Unless things that changed, all those markers are placed by users with no AC verification. So you can put a marina or a hazard anywhere you want. I am sure that the users try to do their best but they arne’t cartographers.
I think the marinas are verified. Possibly not the anchorages and hazards. I usually don't pay attention to the "hazards" because of the often low quality of the reviews. What may be a hazard for one boater may not be for another boater. As far as anchorages, it's possible to anchor in lots of places not identified on AC or a book.