The day you want to leave, you have to see the gendarmes to stamp your passports. They will give you a custom form (the white, green and pink form), the gendarmes will stamp the 3 forms. The green and the pink forms are for you, as for the white one, you will have to put a stamp on it, and post it. Before, you post the white form, you will need to scan or take a photo it and send to your agent so that we have a proof of your departure.
If you fail to post your white form, your boat will be considered as still in French Polynesia water and if one day, you would like to come back you might have problem to do so.
You can go to the Maikai Marina to scan your papers.