Each increase in rank requires higher levels of on the boat experience.
Crew Rank only requires crew experience
Skipper Small Boat Rank (25 feet and smaller) experience requires small boat experience
Skipper Rank (large boat (25 ft and greater) requires sufficient experience on 25 ft (7.5 m) or greater
Bareboat Charter Master Rank requires experience sufficient on a 28 ft (8.5 m) boat
Captain Rank is the same as Bareboat Charter Master
For complete information see https://www.nauticed.org/faq-sailing-certificate#sailinglevels