What's underneath the surface in this archipelago - the world's largest - brings new meaning to the old expression "the scientists are baffled." That's because in addition to the thousands of varieties of fish and coral, divers are finding unidentifiable marine life in the blue, in the muck and on the reefs, that naturalists are hard-pressed to catalog.

Within 17,000 islands, Indonesia has almost 15 percent of the world's coral and about 25 percent of its fish species. Is it any wonder why Indonesia - occupying roughly the same geographic dimensions as the entire Caribbean - is arguably the world's hottest dive destination? And if you're the avid diver you think you are, wouldn't you think it petty to complain about the 24 hours it normally takes to fly to Bali, the storied, idyllic gateway to this undersea Eden?

It's impossible to savor all of Indonesian diving on one trip, so you've got a premade excuse to return another day. And what tempting options: muck diving for macro life in the Lembeh Straits or Sangeang Island; testing your fish ID to the limit on Raja Ampat, Kri or Misool, in the heart of the Coral Triangle; cruising on a live-aboard from Bali to Komodo, or between Flores and Alor, or northern Sulawesi and the Sangihe Islands; or diving 24/7 from an over-water bungalow in Wakatobi.

In Bali, whitewater rafting, tramping around rice terraces, taking in time-honored cultural dances and feasting on babi guling (traditional roasted suckling pig) are all possibilities. Other Indonesian islands have more isolated villages where, if you practice proper etiquette, you'll be enthusiastically and warmly welcomed.

Dive In

Weather - The dry season runs May through September, the wet season November through March, and expect hot and humid conditions year-round.

Average Water Temp - Typically in the low to mid-80Fs, though cold upwellings can reduce water temps in some areas.

Average Visibility - Highly variable, but normally 50 to 100 feet in the most popular dive areas.

Topside Diversions - The exotic, mystical sights and sounds of Bali, its rice paddies, the hustle and bustle of Jakarta, traditional temples, the "dragons" of Komodo.

Travel Savvy - You'll need a valid passport (one at least six months before expiration) and tourist visa to enter any of the countries surrounding the Red Sea. ... Dive shops and live-aboards tend to be hotel-based.

Getting There - Singapore Airlines and Garuda Indonesia are the region's two major carriers, with flights into Singapore, Jakarta and Bali from Los Angeles, San Francisco, Vancouver, Honolulu, New York and Newark. A flight from Los Angeles to Singapore normally takes about 18 hours. Shorter hops will take you to locations throughout the archipelago.

Destination Links - www.indonesia-tourism.com.