I’m sure you can do this in a few countries but my experience was in Mauritius.
Not a lot of special equipment is needed (they provide everything anyway). Just a pressured tank helmet which is supplied oxygen through a tube that links to the boat, a weight belt, sand socks and food to attract fish. Oh, and your flashiest smile for when they take your photo and charge you for overpriced pictures as proof of the experience.
Apart from snorkelling in some exotic beach, this is probably one of the best underwater experiences especially for non-swimmers. It’s good to know though that cloudy water means the environment is rich with food for the fish. It’s just not so great for seeing lots of fish beyond 100 meters.
Also if your swimming costume doesn’t cover your body much (take note, men), you may be vulnerable to fish bites, which is what happened to a Caucasian man on our boat. Not painful apparently as they’re just nibbling, but you’ll end up with tiny pink dots all over your body. I’m sure he recovered.