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