[wdfifteen]

The creepy crawlies thread got me thinking about this. I'll bet there is another thread here about it.
For me -
I went snorkeling on a reef off of Cozumel. Some dumb kids were running the boats. There were 5-6 boats with 6 of us on each one, taking us to a reef about a mile from the beach. The deal was they were supposed to drop us on the reef and go to this place where there was just a grass bottom to anchor and wait for us. The kid driving my boat took us straight to the anchor point and let us off the boat. Apparently he kicked back for a nap. This was a channel through the reef where the water went in as the tide rose and flowed out as it ebbed. It was ebbing, so we were washed out into the Gulf. I was in the water looking at the bottom wondering why this "reef" looked like an uncut lawn in a windstorm, when I popped my head up and looked around - nothing. NOTHING! I could not see a thing but sky and water. It eventually got resolved (one of the boat drivers figured out what happened and came looking for us) but I was one terrified dude for a good half an hour.

But maybe it was -
I had about 10 solo hours and went up to get some seat time. The weather called for increasing clouds moving in, but I was only going to fly around for an hour. I headed east and encountered a cloud bank, so I did a 180 and headed home. The clouds got thicker, and I realized the cloud bank wasn't moving horizontally, it was descending. I knew the area well enough to know there was a grass strip somewhere between where I was and home, if I could only find it before the clouds hit the deck. I found it in spite of the fact that a Piper PA28 isn't the best for looking straight down. I landed safely, but I was down to about 100 feet before I found it.