American Flag upside down?

[Brite Idea]

I'm heading back home yesterday and as we pass Gilgo in the SBC we slow down heading into the marked 5mph zone. Well I see a boat in front of us under power heading west and there's a guy in the cockpit holding an American Flag on a flag pole upside down and waving it at people. My wife says to me "why is he doing that?" I said I don't know but I know who to ask. So, why was this guy holding the flag upside down?
Rob