The French authorities have provided official clarification regarding social security payments for yacht crew.
The document, provided in French and English, has answered the question of how French residency is determined (more than 6 months in total during a 12 month period), and also specifies that time spent in the shipyard does not count towards the days you have spent in France / French waters.
It also confirms that you do not need to subscribe to ENIM if you can show that you have suitable equivalent insurance from a different provider in place.
Please do take the time to read this document.
We are grateful to the French authorities for providing clear explanation and for being receptive to the negotiations from the yachting industry.