Rescue swimmers in the Coast Guard have to be a tough lot. That’s even more true for female rescue swimmers. There are only four of them in the service, and that gives you a good indication of their caliber. In April, we wrote about Aviation Survival Technician 2nd Class Jaime Vanacore, a rescue swimmer who was trying out for American Ninja Warrior (she got invited to Las Vegas for finals, by the way) and now Chief Aviation Survival Technician Karen Voorhees has made history by becoming the first female rescue swimmer in the Coast Guard to make chief. She was…