The French authorities have now clarified the criteria for payment of social security contributions by yacht crew operating in France and French waters.
Firstly, you are considered resident, and therefore liable for social security contributions in France, if you spend a total of 6 months in France (or French waters) during a 12 month period.
Secondly, the time spent in a shipyard in France does not count towards the time you have spent in France (or French waters).
Thirdly, yacht crew do not need to subscribe to ENIM if they can provide evidence of a suitable equivalent insurance from a different provider.
You can read the full statement below via the Professional Yachting Association who have expressed thanks to the French authorities for being receptive to negotiations with the yachting industry.
Clarification on Application of Article L 5551-1 of the (French) Transport Code