What's the plural form of yachtsmanship? Here's the word you're looking for.
Answer
The noun yachtsmanship can be countable or uncountable.
In more general, commonly used, contexts, the plural form will also be yachtsmanship.
However, in more specific contexts, the plural form can also be yachtsmanships e.g. in reference to various types of yachtsmanships
or a collection of yachtsmanships.