My son (who was 14 at the time) and I went diving twice on a DCL cruise. In our group I would guess the majority of people were in their 30's and 40's. There may have been a few in their 50's or early 60's.
I did not get the impression that the dive companies weren't super strict on the rules. For instance, my son was a junior diver at the time and yet he was allowed to go below 70 ft on one of the dives. My guess would be older age is not an issue, they would let the individual decide if they can safely dive.
I know some cruise lines have maximum ages, I just couldn't find anything listed for Disney.
My dad will be 73 soon, but he is an avid diver (over 300 dives, didn't start until age 65).
He gets so offended at the age limits given by some cruise lines, ha!
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