This reminds me of a story. I have always loved Nessy and the Loch Ness Monster has always been one of my faveoirtes.
Up in Lake Tahoe where I go every year for vaccation in the summer, they have a kind of joke myth, called Tahoe Tessy, though unlike the Loch Ness it is not really meant to be taken seriously but just in a bit of fun, but as a kid I use to like to beleive it was true.
So anyway one year when I was up there, It was maybe 4 or so years ago I was swimming in the water, and there is this big post in the water that is meant to divide the area between where boats can go, and where swimmers can go, and I always swim out to it every year.
So I swam out to the post, and was just resting there a moment, when I looked down, and just saw this huge shadow under me and there was not anything around just the sky above, but nothing else that could have really caused or cast a shadow, so always liked to think it was Tessy, but when I saw that, I just turned around and swam to the shore as fast as I could