You probably already know that a ship’s speed is measured in knots (as is an airliner’s). A knot is one nautical mile per hour, which is 1.15078 miles per hour, according to Google. An average cruise ship may do 18 knots while cruising, if it’s moving quickly. So, you are spending your vacation going just under 21 miles per hour. This will make highly active people crazy, which is (I think) why there are so many distractions on a cruise ship. I find the pace relaxing.
I used to take train rides for vacation, and Amtrak’s maximum speed was 78 miles per hour on good tracks. (There are very few good tracks.) I used to think that was slow, especially compared to how my fraternity brothers drove in college.
Twenty-one miles per hour is pretty slow. (A human’s maximum running speed is 27 miles per hour, but it is difficult to run on water.) It’s why it takes eleven days to cross the Atlantic and then takes eleven hours to fly back. For reference, the last time I was on an airplane, we were doing 20 knots while we were taxiing to the runway before we even left the ground.
I just checked (because I’ve been meaning to do so), and the maximum speed a clipper ship achieved (according to Wikipedia) was 22 knots. So, when you replace sails with three or four diesel-electric engines, you really don’t go much faster. This has always interested me. We can go faster on land with cars than with horses. We can fly now. We’re still going the same speed on water. However, we now have restaurants, bars, pools and possibly a bowling alley. Clipper ships had cargo and not much else.
No matter how slowly they go, you will probably travel quite a distance on a week-long cruise. Just don’t expect to travel very far on any given day. You’ll go about 300 miles overnight, for example.