I don't see how someone that can't swim can snorkel.
I'm not surprised, but it's true, even if you don't understand the process. I've known several folks who could snorkel, but couldn't swim. I was one of them, I taught myself to swim as an adult. Prior to that, I found snorkeling to be extremely easy, even without a vest. What makes snorkeling easy for a non-swimmer is not having to concern themselves with breathing which lets them leave their heavy head down in the water as well as the fact that fins push you through the water much, much easier than feet.