Quick answer. Croatia is in the EU. If you are an EU, EEA or Swiss citizen you can work here with no permit. Everyone else, including UK passport holders, needs a residence and work permit sorted before the job starts.
Do skippers and crew need a work permit in Croatia?
EU, EEA and Swiss citizens do not need a work permit. If you stay longer than 90 days you register your residence with the local police. Everyone else needs a combined residence and work permit, which the employer applies for through the Ministry of the Interior. Arrange it before you travel, not after you arrive.
Does the type of yacht matter?
On a bareboat charter (a yacht for up to 12 guests who charter it and hire a skipper) the rules above apply, because you are providing a service locally. On crewed charter, private yachts and superyachts, crew are often treated as seafarers and the route can differ depending on the flag and whether the yacht is based here, so confirm for that specific yacht. Working ashore follows ordinary work-permit rules.
Official source
Croatian Ministry of the Interior (MUP) for foreigners and work, and the Ministry of Foreign and European Affairs for visas and residence. Confirm the current rules for your nationality before you travel.
What we ask of you
Keep your nationality correct in your profile; it tells us your EU status.
If you hold a work permit for Croatia, 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 Croatia if you do not hold the right to work. See also: Visas & work permits, overview.