Quick answer. Montenegro is not in the EU, so there is no free movement here. Everyone who works, including EU citizens, needs a residence and work permit. Visa-free entry (for many nationalities) lets you visit, not work.
Do skippers and crew need a work permit in Montenegro?
Yes. Whatever your passport, working in Montenegro needs a temporary residence and work permit. The employer applies through the Ministry of the Interior, and the permit is usually valid for a year. Sort it before your dates, because a tourist entry does not give you the right to work.
Does the type of yacht matter?
On a bareboat charter (up to 12 guests who charter the yacht and hire a skipper) the rules above apply. On crewed charter, private yachts and superyachts, crew are often treated as seafarers and the route can differ with the flag and where the yacht is based, so confirm for that yacht. Working ashore follows ordinary work-permit rules.
Official source
Government of Montenegro, including the Ministry of the Interior, and the public-service guide to temporary residence and work. Confirm the current rules for your nationality before you travel.
What we ask of you
Keep your nationality correct in your profile.
If you hold a work permit for Montenegro, tick the work-permit box.
Tell us early if your right to work is not sorted, so we can help before your dates.
Important
Immigration rules change and vary by nationality. This is general orientation, not legal advice, and Quarterdeck is not an immigration adviser. Confirm your own position with the official source above before you travel. We will not place you in Montenegro if you do not hold the right to work. See also: Visas & work permits, overview.