Thanks for the suggestions. I've heard about Virgin Gorda and Little Dix Bay. How does the diving compare to Bonaire and Little Cayman ? (I know - nothing quite compares to Bonaire)
Most of the better diving off Virgin Gorda is a short boat ride elsewhere. In a week of 4 dives/day we only dove one site directly off VG, the Aquarium and it was a shallow 2nd dive (lots of fish obviously)
Diving isn't quite up to Bonaire standards, when we were there in late April the vis wasn't much above 70' or so and there were often particulates in the water. It's partly because the islands are between the Caribbean and the Atlantic so in some areas the currents and tidal exchange affect it.
It's also however a great spot for larger stuff. Almost every dive we saw small sharks, turtles, cuda and some larger ocean-going fish. At one dive, we dove a above water pinnacle, one side was the Atlantic and the other was the Caribbean. Since it was sheltered there were thousands of tiny baitfish. I watched as several cuda and a couple of smook? hit them repeatedly - silver scales everywhere...
There's two prime areas that we dove from VG, the Dog Islands slightly NW (VG is a long island) and all the channel islands to the SW - Cooper, Norman, Salt, Ginger etc.
IMO the Dogs had less fishlife but larger stuff. Also less bottom cover. The SW islands had a profusion of soft corals, sea fans etc, with lots of smaller fish hiding around it. Also we only saw turtles there afaik. Nowhere were there massive schools of fish but always something interesting to look at.
If you're familiar with the Vista Blue area on Bonaire, it's closest to that but with much more vertical rock formations and hard ledges. The islands themselves are very vertical and drop into the ocean, it continues below water. Some of the better dives - Thumb Rock and another I can't remember - were big rocks thrusting out from the reef. It's pretty impressive. Generally we never exceeded 70-80' all week and were near/on the bottom.
One must dive is the Rhone wreck. I'm not a wreck diver (I'm the guy that always votes reef over wreck on the boat) yet it was the best I've ever done. The front 1/2 is a long swimthrough - it's where they filmed "The Deep" and the back is just full of all kinds of interesting stuff, a huge driveshaft leading to a massive propeller - it must be 15-20' tall, lots of small stuff embedded in the coral, collapsed structure with intact glass portholes etc. They move the boat between dives as the moorings are somewhat far apart. Dayboats from Tortola and even St. Thomas also dive there. It's about the only time all week we shared a mooring.
The DiveBVI folks are a great group. It's one of the few diveops that actually do what they claim. We literally gave them our gear at the beginning of the week and picked it up cleaned and dry the following Sat. Every day everyone's gear was laid out down to the tiniest detail, we were even asked how we wanted things configured. Every night they stored it - I don't know the arrangement at Little Dix, it's not their main location.
If you do stay there, plan on going to the Baths one day to snorkel. It's these gigantic rock formations rising out of shallow water on/off the beach. google it, they're pretty famous.