I had a tenant that was first officer on a British liner in the 50's. The crew matched the passengers one to one. One the cruises I've been on the passengers out number about 3 to one or 3.5 to one.
My observation of a Norwegian Cruise liner taking on drinking water in Mexico, makes me think there is a reason for sick ships. The ships I've been on take ALL their drinking water from the ocean and treat it onboard. The first I was on had 4 treatment plants, the second had 5 or 6. I was prepared to only drink bottled water but the treatment operations did a good job. The one Royal Caribbean ship that became about 25% sick, had a flu outbreak. Coming home on the plane from the last cruise, I sat next to a Hooker sick with the flu and forced my wife to take care of me for three days, since I protected her! So you can get sick with the flu anywhere.
The topic at hand seems to be the graceful lines of ships from before the 70's verses the comforts and features of the floating resorts. When we pulled out of a Mexican port, a 400+/- passenger ship that looked like "The Love Boat", was pulling into port and being tossed on the waves. I really prefer the stabilizers!
Ivan