Nasty deer flies

We went cave diving in a remote spring in central Florida. While we were hanging out by the spring we kept getting attacked and bitten by horse flies. Now my girlfriend has huge red welts that oozed A liquid puss that seemed to crystallize after it hit the air. Here are the pictures 

We treated the bites with alcohol and calamine lotion. I also received bites but none of them got this bad. I was able to kill many of the flies as they landed on me  and I tried to stay submerged in the water to keep them away.