I'm a newbie and just did my first ocean diving at Grand Cayman a week ago. We dove with Indigo Divers the first day - did two 2-tank dives (morning and afternoon) and I had a great experience. We did Little Tunnels, Doc Poulson, Big Tunnels, and Peppermint Reef. Chris and Kate have a very nice but smaller boat, and they take no more than 6 divers. Very friendly and great to work with.
We did a 2-tank dive with DNS a couple days later (Indigo was booked). Dusty was great and his boat (8 diver max) was much larger and very comfortable. We really had a great experience with both and they both pick up at the Marriott at 7:15 am. They stuck to the west shore for all dives. We wanted to do the north wall but they said the winds would not permit and come back in the summer for a north wall dive. Oh well, I really loved every single dive and saw tons of fish.