If you join the boat first, then go through the Capitaine du Port, the Port Captain
, and he will inform you whom to contact and what to say to import
goods for a "yacht in transit". At least that's how it works in New Caledonia
, French overseas territory.
Otherwise, contact the Douane (Customs) directly, tell them what you want to do and that it is for a yacht in transit to Australia) and see what they say.
Another alternative is to ask someone from Alliance Francaise to help you write a letter (in French) to the Customs
and start there.