I was talking with some dive buddies the other day and we ended up trying to answer the question, "Where would you dive if you could only dive one place?" Well, that question was tough and there were some battles in different directions that were as funny as they were pointless. The discussion did inspire me to come up with my list of picks if I could dive only four places (not including local sites). I felt that it would be most appropriate to try to come up with four sites that offered different things so I could get the most our of my own "Final Four."
Toward the end of World War II, allied aircraft attached the Japanese Combined Fleet while they were anchored in Truk Lagoon. The result is a wreck diver's paradise. There are over 50 ships sitting on the bottom - many of which are well within recreational limits. Some of the smaller boats and numerous planes that were shot down are shallow enough for snorkelers to investigate. There are many world-class wreck dives in the lagoon, and I am sure everyone has at least a few favorites. One of the common standouts is the Fujikawa Maru, an aircraft ferry that still has planes in its easily accessible holds. Other wrecks have trucks, tanks, and other heavy machinery still strapped down.
Great Barrier Reef
The world's largest reef may be stretching the definition of a "spot" - it is 1,500 miles long and encompasses over 100,000 square miles of diving area. That's part of what makes it a good choice on my list. Also, the Great Barrier Reef has TONS of aquatic life to see. There are over a thousand different species of fish. It's got sea snakes (not my favorite), sharks (not a big fan of those either), rays, turtles, monstrous grouper, dwarf minke whales, and beautiful tropical fish like Nemo.
The Yucatan Peninsula is riddled with underwater caves and their sinkhole openings called cenotes. It is hard to pick a single "best cave diving" location, but it is impossible to overlook the area around Akumal as a candidate. The water is typically crystal clear and doesn't have near the current that many of Florida's spring fed caves exhibit. The water is warm for caves - around 75 degrees. New caves and passageways are being discovered all the time - that's right, you can still EXPLORE here! The Mayans viewed many of the cenotes as gateways to the spirit world; and, there are amazing artifacts that can be seen (seen, not touched or taken) while diving. Many of the cenotes are surrounded by dense jungle and can really only be reached by divers who entered the cave system at another cenote.
I am one of those crazy (or just stupid) guys who truly enjoys ice diving. There's something wonderful about cutting a hole in the ice and diving in to see what lies in the clear waters underneath. I wouldn't want to give up ice diving all together and my other spots are a bit too tropical for ice outside of a drink, so I figured why not go all out and head to McMurdo Sound. There are only a few companies that run dive charters to McMurdo, but they do exist. Visibility is amazing: 500 feet is common. There are plants and animals that live only in the waters of Antarctica. Oh, speaking of the waters, the water temperatures are as cold as 28 degrees. These cold waters actually help many species grow to huge sizes that are unseen anywhere else.