Papa has a small white square in the center of a blue background, and it stands for "P" in the signal flag alphabet. I'm really trying to come up with something interesting to say about this one. But if it's the LEAST remarkable of all the flags, I guess that makes it notable in its own right. Apparently it's also called The Blue Peter but I don't even want to get near that.
Ships at port that are getting ready to depart fly this flag. Basically it means "Get on board now or you might get left behind." This is a good signal to have, and I'm willing to bet it led to a HUGE decrease in sailors being left places.
If you see it out in the open water, it's likely a fishing vessel that has its nets caught on an obstruction. I'd imagine this is to give you a fair shot to come over and laugh at their misfortune.
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