Since I hardly do Facebook, I don't know what they have listed for email address. But this is the one that I have for THE guy who coordinates pretty much everything on land, including bookings. He seems to be one of those people who knows everyone and everything that goes on in Rurutu. His name is Teiti.
teiti.tavita@gmail.com
Actually, I did not book with them beforehand. I booked with a different outfit, but their local rep who was supposed to take us out was, to put it mildly, irresponsible and unresponsive. As a result, our first day out was with Vaitumu's (our lodging) own operation, and while we loved their service and their boat, they were unreliable: on our second day there, they said they couldn't take us out.
Teiti learned of our plight and we were able to go out everyday without a hitch that afternoon and the rest of the days we were there. It is a family-run operation and they have multple boats - that is also a plus.
Should you not get a prompt enough response, I can also suggest emailing Gisele, his aunt (I think). She has a place available for lodging. When I could not find lodging at Vaitumu for a couple of people in my group, I emailed her and she was quite responsive; so I am guessing that, if necessary, she can get you in contact with Teiti. Her email address is:
tavitagisele@gmail.com
I am one of those who books trips close to a year in advance, if not more, so I am not the person to ask about how far in advance, altho the fact that Teiti was able to easily accommodate us on the spot suggests that it doesn't need to be very far in advance. On the other hand, traveling to French Polynesia is never an inexpensive proposition, and it would suck to get there and twiddle one's thumbs. I like the peace of mind of going there with something in hand.
If you have further questions or want more details, feel free to ask. I often get accused of writing too much (in fact, I already did), so I did not get very deeply into the nitty-gritty of the above.