As I've never been in Niolon, I can't answer exactly.
However, what you can do is to write to
flabelline@caramail.com and say her how and why did you get her adress (Her name is Nathalie and I'm Juan,
fbbomao@caramail.com). Her father is a scuba instructor and he probably will able to help you. If not, I've more friends, but it will get more time to got their e-mails.
The visibility depends again of the day of currents and waves, but I think that not many more than ten meters. Concerning your 3 mm... good luck.
Living in Florida, why do you want to go to France!? And in winter!
If you need contacts, I can maybe help you. I've already worked in Saint-Raphaël, and dove in Cannes, Saint-Raphaël, and the Marseille area, but I think I can give you a couple of phone numbers.
On wednesday, I'll fly to La Palma, a Canary island, until 25-S , so I won't be connected, I'll be diving all day

in blue, clean and warm water. If you want to send me a message, better tomorrow.
And I've heard a great shark's been seen around the island twice in some days... Maybe a white shark...? They're talking about 4 meters at least.
J.
P.S: Nathalie speaks good english.