*Answer for anyone wondering later down the line, went in 2024 for a month*
The diving is good in Nosy Be & surrounding areas.
There's a wreck dive relatively near shore thats excellent. Thousands of fishes swirling around it & dozens of scorpion, stone, crocodile & lion fish all over it.
Many very good dives in general!
You can snorkel at Nosy Tanikely, which is very good snorkeling, but you can also do it as a dive trip & the dives around are excellent!
Nosy Sakatia is a small island with a dive resort at a tip that's very good. They have a few types of great turtles feeding right by the lodge (you can swim to the area or they drop you with a small boat) & you can snorkel nearby. It was very nice & you can go early or later outside the activity hours of the people going as a trip from Nosy Be.
We had good diving experience with Tropical Diving.
We didn't dive with Oceane's Dream, but chatted with some of the staff/manager/dive master? and he was very friendly & helpful without having us as customers. I think they are probably a good outfit.
There's very few liveaboard offerings (smaller boats for 2-6 divers?) & seems like a custom trip), but those should be excellent on the farther archipelagos!
The waters around Nosy Be are super flat & quiet. The boats don't even have a back board on the boat.
If you are used to the rough Southern Africa dives that are beach launches in waves & swell, you will be very happy with the relax diving of Nosy Be.
Enjoy!