Dwayne is the expert on Carnival, thank you so much for posting
They may let you take him as they usually do not ask for proof of age. Does he know how to snorkel? The catamaran ride would be fun for him, but he'd be pretty bored if he couldn't go in the water. Do you feel safe letting him in the open water? Would you feel safer having him in Camp Carnival? They do a marvelous job with children and usually the children don't want to leave. Just some things to think about. Personally, I learned how to swim when I was 7 months old. However, my dad didn't let me go on an open water snorkel until I was 7. My parents did let me play on the beach and in the water, as long as one of them were with me.