With sea star.... we stayed to the north.... there were not a whole lot of divers with us, so we were able to go to a place called lovers tunnel i believe. Rick... was our dive guide. Awesome guy. The the owners brother has a restaurant on the island as well that served some awesome breakfast.
We stay on the south end of the island so for the first 2 days with Blue Heaven, we went to tackle box, and stayed around that area. saw lots of nurse shark, eel, some barracuda, and even a few black tips.... For HolChan... its shallow, but I did it at night.... very cool, but lots of people were there. At night we saw a lot of eagle ray... They like the bubbles, and light.
When we were diving with SeaStar... We saw a HUGE Mantaray.... they said it had been hanging around and they had seen it before...
We didnt book in advance just so we could golf cart it to different locations instead of making it a longer boat ride. You might ask them about a night dive at Holchan your first night there too.