It seems as though the upper level cruise ships have age limits on excursions. Recently booked a Celebrity cruise and they limit some dives and hikes to the age of 60. Royal (who owns Celebrity BTW) goes to the same ports and don't have an age limit. I generally book directly with dive shops while on cruises and never (yet) ran across an age limit. I do typically just answer NO on all the medical questions as it burdensome to explain every medical issue I've had, none of which affects my ability to dive.