Walls are the name of the game here in this British Crown Colony—great plunging cliffs that sometimes begin in 50 or 60 feet of water and take one giant step off the continental shelf, out into the great eternal blue.

That's because the Turks and Caicos are low-lying limestone islands perched atop geological platforms that rise impressively up from the ocean abyss. Geographically a part of the Bahamas, they are culturally separate, in their own little world down here between the southernmost Bahamas and Hispaniola. There are seven major islands—two of them uninhabited—and 40 smaller cays.

With virtually no nearshore run-off from rain or streams, no mountains or even hillocks, the visibility is consistently outstanding—indeed, it characterizes this island chain as much as the plunge of the walls.

But there are other draws as well—including the offshore spur-and-grove coral reefs and snorkeling-friendly, shallow patch reefs (just off the beach), one giant blue hole on the banks south of Middle Caicos and—on the distant southeasterly Muchoir and Silver banks—schools of seasonally migrating humpbacks. And there is Jo Jo, a human-attenuated bottlenose dolphin known to get up close and friendly with divers whenever he feels like it.

This island-nation was one of the first in the wider Caribbean Basin to pass laws prohibiting spearfishing years ago, and today that conservation has paid off with larger and healthier fish specimens than found elsewhere. Marine parks, like the Princess Alexandra National Park on Provo, now extend over many of the dive sites, protecting both sunken historic shipwrecks as well as the pristine marine life—even shell collecting is prohibited. Mooring buoys, pioneered years ago back in the Keys, mark key dive sites. And thanks to the reseeding of local waters by the Caicos Conch Farm on Provo, these islands probably have some of the healthiest population of queen conch you'll encounter. Topside, ruins of Loyalist plantations and old windmill-driven salinas can be found; as for industry, commercial fishing has long been replaced by tourism and offshore banking.

Wall-wise, the best site on Provo is Northeast Point; the uninhabited island of West Caicos—a bit of a longer run by boat—is more than worth it.

Serious divers were the mainstay of tourism here two decades ago, enjoying the bargains of modest local hotel dive packages, the exceptional diving and not much else. Today, the world has caught up to the Turks and Caicos—particularly on the busiest island of Providenciales ("Provo") which seems to be gentrified in the theme of South Florida. Grand Turk, more remote across the deep Turks Island Passage to the east still retains its Brit flavor, though.

These islands are quite clearly accessible—just a 90-minute jet ride from Miami. Airfare is not the expense it might be in more remote locales. Once here, there are plenty of dive shops with packages that include hotel stays—by far the best deals. Still, everything but seafood must be imported, and even that is not cheap—this is the Florida Keys, except with food and drink prices from one-and-a-half to double what you'd pay there. The good news is that conch here is fresh from the shell, tasting unlike anything freezer burnt you've ever had.