3 concentric squares, blue, white, and red from the outside in, make up Whiskey, which stands for "W" in the signal flag alphabet. It's slightly disconcerting that the pilots who came up with these names were so fond of whiskey, but I think hope they've tightened up the rules around that.
Whiskey is a request for medical attention, so it's a more specific version of Victor. I'm willing to bet that back in the day whiskey was the cause for some of these requests. If you have a medical emergency onboard your megayacht, this is probably a last resort. Try the radio first, or a satellite phone. Or just take your helicopter back to shore.
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