"Hey, barn doors open" usually does the trick. If you want to be classy you can say "your shirt is coming untucked in the front." People generally look down at their belt line when told that in my experience.
@ArashL thanks, I can't take credit though. One of my old college professors taught me that. He was a very classy gentlemen.
@jayneonacobb You can take credit for learning manners though!
I've never found another way of saying "Your blouse is unbuttoned" to a women though?
"XYZ, dude."
Haha! That's what I was going to say but I didn't think anyone would get it!
@ArashL Bingo! You get an "A"
"You're flying close to the wind" is a euphemism used in the UK
You could try, "You might need a much bigger stick if you're planning to play pool around this place."
That is a good question. I go to a local hot spring and there is an elderly gentleman that always has part of his junk hanging below the hem of his swim shorts. It seems like that is something a guy would notice but he does not seem like a freak in other ways
Had this happen with a friend in a rowboat. I just couldn't say anything because I'd have had to row us back.(And I rowed us out). rofl I guess maybe they don't know?
We'll have to ask the men,
My zippers have a mind of their own. However for a woman wanting to strike up a conversation with a man, it's a good pick-up line. But if a man should tell me, I'd probably wonder why he noticed. Personally I have never looked at a man's zipper. Nada, not once.
Simply walk up close enough to quietly tell him. He will appreciate knowing.