I took that little boat four through the Okefenokee Park one day with my wife, they about toted us off. There was a little black bear on display they were eating him alive.
Okay they don't have them in great numbers where I do outdoor activities, so I had to google them. Is this the type of yellow fly? They sound mean & nasty.
https://entnemdept.ufl.edu/creatures/livestock/yellow_fly.htm
They're up here in pockets. UnfortunatelyThat must be a swamp thing!