Honestly the last one needs to be a thing for so many reasons. I had an experience in the Florida keys a number of years ago that has stuck with me. I was on a snorkeling charter and some foreigners were aboard [of Asian decent]. (I've included their race here just for context, not racism, as formal swimming lessons overseas are not nearly as common as they are in the USA). I was near the front of the boat on the second level when I saw someone splashing. I had a small flashback of what a swim coach had told me at 13 years old: Drowning does not look like drowning in the movies. I yelled that captain who was setting an anchor, and the first mate who was helping tourists put their fins on. Both looked confused what I was trying to signal through the bussle, so I dove off the second deck and swam to the person. He was under before I got behind him, so I yanked him above water by his un-inflated vest and tipped his head back over my shoulder. He rapidly tried to pull me under so I had to restrain his arms with one hand and inflate his vest with my other hand and mouth, while treading with just my legs. Scariest 10s of my life, but it was over that quick once I got a little positive buoyancy into his vest. The current had pulled us about 35 yards from the boat at that point so I had to swim towards the boat a bit to grab the rescue line. Captain and first mate thanked me profusely. The guy couldn't speak english and didn't realize he needed to wait in line for the first mate to check everything (including vest inflation). Instead he just jumped in off another part of the boat. The tour company gave us a refund and bought us dinner.