Thats what two drunk guys asked me while I was diving in Michigan on an inland lake. I had been down about 50 feet and was aware there were boats zooming around above, but on my ascent I stopped at about 15-20 feet and relaxed for a couple minutes and as I did a boat drifted right up to my flag using a little trolling motor. I came to the surface about 20 feet away and somewhat politely asked what was wrong, and they said they were just wondering why there was a tube floating with a flag in it, they thought it had got away from shore and were going to take it into the beach! Just thankful I took my time coming up!