Would like to book an excursion to the reef from Key West, FL. Husband is a weak swimmer but has snorkeled twice in sandy bottom beaches, with no more than 5′ of water. Has also snorkeled twice in cenotes of the same depth. He feels safe with a life vest, and either excursion I’m looking at provides that with instruction and hands-on guides.
Bottom line, which a safer, easier, experience for a non swimmer, Snorkel or snuba? This will be in open water which will be a different experience for him.
Note: I’m referring to sNuba - where you breathe through a scuba regulator that is connected to an air tank which floats on the surface - not scuba.
Neither are truly safe for a non-swimmer. Most excursions/tours will take for granted that you can swim when setting up snorkeling tours. They usually go to safe enough places, but really snorkeling over a tropical reef requires far more swimming skill than you seem to be describing.
I don’t want to disappoint you, but even the most tourist oriented dive trips will require that you complete their training to become a "certified" diver. That would include trips where you use a fixed air supply instead of an air tank.
I hate to sound too negative, but I am a realistic (and an ex-life guard, who has been an ocean swimmer for over 50 years), and I don’t believe that any open water trips are appropriate for people who would class themselves as non-swimmers. A life vest is a help, but believe me, not guaranteed to keep someone who is a non-swimmer safe. There are lots of other fun things to do in Key West. beers at Sloppy Joe’s are sort of a water sport, right?