I've seen it do that up in Town Creek a few times over the years. Once there was a huge release that almost looked like the boil below Guntersville Dam. It was about halfway between the bridge and the power lines. It made a hump on the surface that looked to be about 6-8 feet in diameter and about 4-6 inches high. I've never seen anything like it before that or after it. It only lasted for a moment.