We have had a great time dancing on ships, particularly Costa cruise lines. When the cruise ships had teachers, they usually focus on basic stuff, so with 5 plus years of private lessons, we don't go to the lessons. I have stopped and watched them a bit. Instructors vary from poor to excellent. Our last cruise had a couple in their 80's, who still were good dancers and were excellent teachers.
It would be difficult to do anything besides beginner level on a cruise ship.
Since the experienced dancers would be so diverse in style, experience etc..