[Utah-astronomy] Someone pull the plug in the lake?

I was flying over the Great Salt Lake last evening (Friday) a few minutes after sunset when I noticed something in/on the lake I've never seen before. Looked almost like someone had pulled the plug in the bottom of the lake and the water was swirling down. :) I wondered if some sort of giant swirl of air could have created it however the air was quite calm with just a little turbulence. Here's a link to the image. It's just a cell phone image so not high quality but it does show what I saw. Any thoughts on what it was? http://users.wirelessbeehive.com/~paw/temp/gslswirl.jpg