I don't particulary care for nav light on the mast head.
Open waters........ fine no problem. A mile or so distance and there ok.
In shore, close proximity....... most people are watching the water in front of thier vessel and not looking up 40 feet into the night air.
I have come up on boats in waterways at night with the mast head lights and I see the faint shadow of the hull before I see the lights.
I am not a big fan of masthead nav lights.
Courtney is My Hero
If a man is to be obsessed by something, I suppose a boat is as good as anything, perhaps a bit better than most - E.B. White