We were snorkeling with a group of about three dozen people in the Florida Keys today as part of a tour package. My 16-yr-old son, 14 & 9-yr-old daughters joined me for some adventuring on the Florida Reef. We were near the more mundane portion by Key West; this barrier reef extends past Key Largo, and that's where there is a lot more color and variety of coral structure.
Anyways, the group spread out, and about 10 minutes into our group getting into the water, I noticed my son rapidly swimming towards a lady maybe 20 yards from me and my daughters. She'd gotten a few mouthfuls of water, couldn't clear the snorkel, and started to panic. Despite guidance for all of the newbies to add some air to their buoyancy compensators (BC's) before entering the water, she did not, and if it weren't for another husband & wife nearby who initially grabbed her, she would've quietly slid under. They called for help, and my son sprinted over.
Even though it had only been a half minute, the couple were already visibly exhausted trying to help keep this lady afloat, and she was still in a panic, thrashing at the water, wide-eyed and visibly shaken. My son put two lungfuls of air into her BC to raise her torso a little bit out of the water, rolled her onto her back, head elevated, and instructed her to slow down her breathing. That lifeguard training he took this summer for his job made a difference! He started to pull her back to the boat while my 9-yr old and I waved down a rescue swimmer who then teamed up with my son to take her the rest of the way back.
My son works at a pool on the local AFB back home; I don't think he ever thought he'd have to help save somebody in open water.