Mr LtL is very particular when it comes to cruising. He is generally happy (well not complaining) on larger ships (not the mammoth ones like Oasis but the size of Solstice for example). He does quite enjoy a port intensive itinerary as you would find in the Mediterranean, but gets a bit stir crazy if there are more than 2 sea days in a row. He also does not do Main Dining Room well - and we tend to eat in the smaller specialty restaurants or like Pushka in Blu on Celebrity. What he does like though is an adventure cruise with zodiacs for landings and close up wildlife viewing. My avatar comes from Svalbard - from a bobbing zodiac. The arctic was amazing. We keep looking at Antarctica but just not quite got organised yet. He is happy on on small ship for this type of cruise, with a full expedition crew and lecturers. In the Arctic there were some quite mature, well to be honest, they were elderly. passengers on a Captain's Choice tour on the ship. Some of them coped quite well but there was one who was nicknamed 'Miss Marple'. She did keep getting lost and found the agility needed to get into the zodiacs beyond her if it was at all rough.
In response FM, not all cruising is relaxing or for the oldies. There are some itineraries that you need to be younger and fitter to manage.