Well first of all, based on your dive experience, as nice as the Caribbean is as a dive and vacation destination, it looses a bit of it's appeal after diving the coral triangle area... So watch out , as before you know it the rest of your diving holidays will involve 24 hour flights and multiple layovers!
Anyways some comments based on my personal experiences.
#1) Banda Sea, Indonesia. Most people say the Coral Triangle's got the best diving in the world, and most people say Indonesia's got the best diving in the Coral Triangle -- and they don't appear to be wrong. The most popular sites typically seem to be Raja Ampat and Komodo. But based on videos I've seen, I actually think some sites across the Banda Sea are more impressive (and less dove).
Have worked and dived in Komodo, and dived Bali. I think Komodo and Raja probably offer one of the best balances in quality of diving available, and ease and cost of access. Doing one of the Komodo to Raja or vice-versa liveaboard repositioning trips is still on my bucket list.
#2) Central/North Fiji. It's not the Coral Triangle, but there are just colors there that you don't see anywhere else in the world. Fiji, as a dive locale, seems to have been overhyped to the point that it's now underhyped.
Only did a few dives in the Lau island (Eastern Fiji), and that was indeed quite nice.
#4) Southern Egypt (Hamata area). Hard to pick one spot in the Red Sea. Seems like the Sinai Peninsula area might have better reefs, and the Marsa Alam area might have better sharks. But I'd go with the Hamata area if I had to pick one place due to the dolphins.
The Fury Shoals have some beautiful reefs, quite shallow. A bit less in terms of quantity of marine life then other more northern sites in my recollection, but very nice reef dives. I can't recall any dolphin encounters there however. My favorites dives in Egypt would be Daedalus and Brother Island, great reefs, marine life, and chance of pelagics.
Further north to Sinai is great for wrecks, but I found that the reefs are nicer south.
#8) Similans area (Phuket to Mergui). Not quite on the same level as some of these other locales.. but pretty solid!
Yep nice diving, certainly worthwhile if you are in the area. It didn't blow me away to the level that I would plan to go there for just a diving trip.
#9) Ningaloo. The GBR (Ribbon Reefs, Coral Sea, etc.) honestly just doesn't look that impressive to me. I'd rather try Ningaloo.. one of the top 10 places in the world to see Dolphins, Whale Sharks And Mantas.
Not really personal experience, but I'd say 90% of people I know who went to the GBR came back underwhelmed. A friend who did Ningaloo liked it but wasn't raving about it. And he had no luck on the Whale Sharks.
(PS if it Manta's you want to see, Komodo was very regular, and I'd say I had 100% success rate at Manta Point (Makassar Reef)).
#10) Cebu area (incl. Negros and Bohol). This could honestly be #2 on the list, but I wanted to spread things out, and I already had a Coral Triangle locale. The Mindoro/Luzon area also seems top-notch (Puerto Galera, Anilao, Apo Reef, etc.).. but Cebu's got similar diving and Whale Sharks.
Only did some dives at Malapascua (Treshers!, other reefs north of Cebu, and Moalboal, I would say diving there was ok-ish. Would have liked to try Bohol, Balicasag but no time...
Not a big fan of the Whale Shark practices at Oslob, I personally wouldn't support that. I would have a look at Donsol, where I understand it is all done a bit more friendly towards the Whale Sharks.
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Honorable mentions:
-Tufi area, Papua New Guinea. Had two Coral Triangle regions above already.. but this certainly needs to be mentioned.
PNG diving has for me been the best I ever experienced. Diving some of the remote Louisiades was just amazing, blew me away. Also did some diving around New Ireland (Kavieng) which was also good.
PNG has both an big collection of WWII wrecks, and just stunning reefs and marine life.
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Vava'u. The Humpback experience alone garners at least a mention.
Vava'u is a great little group, and beautiful to cruise around in, but the diving was not the greatest. For a better combination of diving and whale watching I'd head out to Ha'apai. There are some very decent dives around there. You'd miss a bit of the green, more rugged landscape of Vava'u with it's beautiful little bays, as Ha'apai tends to be more flatter islands with sandy beaches. But diving is better, and I'd say almost the same chance of seeing Humpbacks. And a small plug for the
Amazing Twin beach resorts in Ha'apai Tonga Matafonua and Sandy Beach run by the lovely
@darrennina, one of the places on this planet I've fallen totally in love with...