It’s just another day in the critter lab. Look closely — between boulders, in the sand and coral fissures. There they are: countless blennies, gobies, seahorses and peppermint shrimp peeking back at masked invaders. Dial back and take in trumpetfish, jacks and a rainbow coalition of reef fish meandering along a dizzying wall. Crayola-crazy corals and sponges smother anything that doesn’t move. Snoozing nurse sharks ­under ledges, turtle flybys, a rare golden hamlet — I could go on. This fertile patch is at an otherwise nondescript site in St. Vincent and the Grenadines, a virtual marine lab of what’s what in the Caribbean. Thing is, you have to recalibrate your expectations here, in reverse. As extraordinary as it might seem, it is purely ordinary — in a good way. At the Friday cocktail soiree where I’m staying at Young ­Island Resort, I gush about the day’s hit parade to Dive St. Vincent owner Bill Tewes. My words barely register a subdued I’ve heard-it-all-before smile. Still, I’m giddy about my first day’s dives. And maybe from the rum-and-Cokes I’m sharing with the man who christened this area the Critter Capital of the Caribbean. About Tewes: To say he’s curmudgeonly is like saying ­vinegar is sour. He’s famously so. “Nitrox?” he barks. “Hell, no. At my shop, we breathe good old-fashioned air. It’s what humans do!” he declares, banging his empty glass on the bar. But I instantly like him. I bet you would too. And chew on this: If you dive SVG, pocket change says you have Tewes to thank. The Texas native is old-school military, and picked up diving when enriched air was a pipe dream, and people drank and smoked like characters straight out of Mad Men. His memories of Papua New Guinea in the early ’80s are fuzzy, but they were the glorious days of dive-travel infancy in the Coral Triangle. Nothing could compare. Almost. In 1984, Tewes landed in St. Vincent, where he bought the only dive shop from a burned-out expat. Over the years, Tewes evangelized the island’s marine life — he’s even documented endemic nudibranchs for scientific annals — earning him de facto Critter King nobility and putting his GPS coordinates on the dive radar. Hovering just south of 70 now, he’s valiantly confronting ­serious medical issues, yet Tewes remains feisty about diving and about life. Most say he’s still synonymous with SVG. He knows it too. And if I don’t buy him another drink soon, I’m gonna catch hell — in a good way. SVG is a place of many places. Burly St. Vincent is the largest and northernmost in the chain, tethering 32 islands and cays swooping 45 miles south like a kite’s tail. Chiseled St. Vincent is dominated by the 4,048-foot Mount Soufriere volcano, yet the lesser Grenadines are Gilligan’s Island-esque. Just seven of these low-profile isles are inhabited and delightfully underdeveloped, marked by scores of lagoons, cays and shoals. It’s an immense waterworld with a trove of named dives and ­unexplored sites. My no-brainer plan: Dive St. Vincent, ­hopscotch south, and get in as much critter time as possible. In the waters of St. Vincent, it’s the little things that count. The Darwinian macro scene is pure alchemy, credited to the Atlantic’s nutrient-ripe currents mixing with runoff from the island’s mountainous interior. On my second day with Dive St. Vincent, we scoot north past the compact capital of Kingstown, along the convoluted leeward coast, in search of macro wonders. The evergreen island is wrapped in dense rainforest, and its mountaintops, obscured by clouds, look slightly foreboding. We pull into a secluded inlet. “Recognize this?” asks divemaster Callie Richards, arms extended. “From Hollywood?” “I dunno,” I reply. “Jurassic Park?” “No, mon, Pirates of the Caribbean, the first movie.” The black volcanic cliff bands, the diamond-dust beach, the lazy palms arching over tourmaline water — it might be more recognizable if this scenery weren’t everywhere. Mental images of swarthy pirates (and raging reptiles) fade when the gentle swells usher us into a sunlit underwater gallery as brilliant as a jewel box. We fin from 80 feet into shallows, where coral-encrusted boulders are elfin housing projects for seahorses, shrimp and anemones. Just before the deco stop, Callie’s underwater eye spots a golden hamlet threading through sea fans. It’s lovely. “They’re super rare,” he says back aboard. “I’ve seen six hamlets in 10 years.” I tell him I saw a golden hamlet yesterday. “Ahh, OK,” he shrugs. “St. Vincent is getting better.” Continue up the island’s Caribbean side, and Buccament Bay Resort looks like the centerfold who crashed the party. It’s a swank new resort with imported paper-white Venezuelan sand, and it’s where I hook up with Indigo Dive’s Kay Wilson, a youngish British expat with her native isle’s trademark wry humor. “Yes, we’re known a bit for scuba,” she says when I ask about the schedule. It so happens that I’m the sole beneficiary of her well-oiled staff; there are no other diver guests at Buccament today. “Bat Cave, how does that sound? You don’t mind little winged furry things, do you?” Kay asks. It might be one of St. Vincent’s most notable dives. But bats? A three-minute skiff ride takes us around the point where the cave reveals itself as a crevice in steep cliffs. Indeed, they’re inside, swooping, screeching, pooping — motivation to quickly descend into the shallow rocky passageway cutting through the reef. It’s a blast. Midway, the eerie dappled light gives just enough wiggle room for bumper-car navigation without flashlights. We’re soon delivered from the rocky womb at 40 feet where we tool through several twisty swim-throughs. Damsels, copper sweepers, angelfish and wrasses lollygag in the surge. With 2,000 psi still in our tanks, we’re macro detectives another ­half-hour, discovering dozens of denizens that slink, slither and crawl. There are other trademark dives: undulating forests of sea fronds at Japanese Gardens, and gorgonians and tube sponges decorating the coral wall at Pretty Reef. My serendipity is the house reef in front of Buccament. With a crescent moon towing a spot-lit Venus, we fin into the warm water, following the cliff walls to 60 feet. The courtship ballet of two cuttlefish fascinates us, and when the shadow of a turtle catches our beams, we redirect our gaze until the turtle dissolves like an apparition. Back on the beach, we sprawl on the sand and stargaze in dead-calm darkness. Nine miles south lies Bequia, first island of the Grenadines. Its tiny town of Port Elizabeth hugs turquoise-hued ­Admiralty Harbour, home to a colorful flotilla of international boats. It is archetypal Caribbean, like a ready-made brochure that could stir a real-estate boom here if Bequia could triple its seven square miles. On this diveless day, I stroll the promenade, mingle with dreadlocked mango merchants, and buy a round of margaritas for people I don’t know. I also mount a two-hour drive, and after postcard shots at every turn, I veer north to the Old Hegg ­Turtle Sanctuary. This self-supported shelter raises and releases greens and hawksbills at three years, buoying survival odds from one in 1,000 to 50 percent. They also monitor beaches, trying to protect mother turtles and eggs from poachers. It’s all a labor of love for weathered owner Orten “­Brother” King, who gave up skin-dive fishing 16 years ago after witnessing turtles killed for meat. I leave with a big lump in my throat and $20 “poorer,” but profoundly thankful that good Samaritans like Brother King exist. Bill Tewes’ influence is never far. PADI Five Star Dive Bequia is proof. Owner Bob Sachs founded the shop after his partnership with Tewes, and with his wife, Cathy, they’ve carved out a sweet life on this little Windward Island. Before our dives I sit on the shop’s porch, chatting with Cathy and her crew. There’s a noisy parrot on its perch, we’re drinking fruit shakes in the shade of royal palms, and there’s just enough breeze to curb the tropical heat. It would all seem preposterously idyllic if it weren’t real. A five-minute boat jaunt from the shop, and I’m headed for the Stratmann wreck, one of 50 dive sites within 15 minutes. Most ­Bequia sites are drifts, beginning in about 20 feet over patch coral that gradually slopes to deeper, multilevel reef gardens. Talk about nonchalant diving. We pour over a boulder reef and intermittent sand flats where critters populate practically every square inch, never mind the French angels, parrotfish and Creole wrasse. The mellow current steers us to the rusted tug, and I see another of SVG’s marine labs, festooned with more than 30 years’ worth of sea life. We fin around the hull that sits perfectly on-keel at 60 feet, watching a couple of spotted snake eels writhing along the sand. Yellowhead jawfish pop from their lairs, and in the background, brown garden eels poke vertically from the sand, undulating in the current like sea grass. As dreamy as Bequia is over the next couple of days, I’m nearly ­giddy when my puddle jumper approaches Canouan, another gem in the southern Grenadines. From the air, the five-square-mile island, its barrier reef, and the distant Tobago Cays look like a constellation of orbiting diamonds, emeralds and ­sapphires. It really is that pretty. The only practical lodging choice here is the wonderfully woodsy Tamarind Beach Hotel & Yacht Club. It’s tucked beneath a hill profuse with tropical botanicals and set along a drop-dead gorgeous strand of beach with its own dock. You can almost fulfill a castaway fantasy here and on the island’s other empty white beaches and walking trails draped by ­crimson-flowering flamboyant trees. I certainly tried. “You don’t look like someone who’s excited to be here,” says Vaughn Martin of Canouan Dive Center. He’s right, sort of. I’m sitting in Tamarind’s palapa restaurant, sipping iced tea after withering from the heat while scouting beachheads too steep to descend. So much for being a Crusoe wannabe. “No worries,” he says. “We’ll have you in the water in no time.” Exactly what I want to hear. For two days, I drift-dive a handful of Canouan’s dives, sites that seem to have just a bit more marine mojo. Take Bachelor’s Reef, a 60-foot drift dive that starts out with a bang on a long, sprawling reef loaded with every coral and sponge the Eastern Caribbean can muster. Southern rays, green sea turtles, moray eels, nurse sharks — all reliable entries on a diver’s checklist here. We also drop in on Steps, where lava flows created a series of geometric steps that lead you through spectacular gardens at 75 feet. The steps are natural, of course, but their uncanny symmetry makes you wonder. My final dive day arrives, and Vaughn has a surprise. I know Canouan is the one-hour nautical gateway to the uninhabited five-islet archipelago of Tobago Cays and its namesake marine park. Any dive in SVG should culminate here. The cays have the most extensive, developed-coral ­structures in SVG, all shielded by the two-and-a-half-mile Horseshoe Reef, which wraps a 1,400-acre sand-bottom lagoon. Sunburned yachties moor here in protective coves. Snorkelers go overboard for the Baradal Turtle Sanctuary and its celebrated population of greens and hawksbills. And for divers, it’s among the greatest shows in the Caribbean. Horseshoe Reef is the stuff of diver dreams. I love current, and this thermal genie whisks us along on a magic-carpet ride that unfolds like an IMAX movie in front of my mask. Vaughn bangs his tank for my attention to see a humongous hawksbill — I’m guessing 650 pounds — sitting passively on a sand patch. A squadron of barracuda missiles hover motionlessly, waiting for something to stir their instincts. In the sand we spot a southern ray, five feet wide, its eyes seemingly following us as we fly by. We later drift the coral corridors and grottoes of Mayreau Gardens. It’s a bigger drift with bigger critters — as in blacktip reef sharks. For our interval, we pay a snorkel visit to the nearby turtle sanctuary and become surrounded by sea turtles of all dimensions, oblivious to anything beyond the bountiful sea grass under their beaks. “Are you ready for the surprise?” Vaughn asks. Funny, I’d forgotten about that. I assumed the pageantry of Tobago Cays was it. “It’s a little something we call Disneyland, sort of our secret spot,” he says of the rarely visited reef jutting from Mayreau Gardens. I pepper him with questions as our boat throttles to this Magic Kingdom. He just smiles a devilish grin and says to wait. He’s right, I’ll just have to wait.

DIVERS GUIDE Average Water Temp:

High 70s in the winter; mid-80s in the summer

What to Wear:

3 mm wetsuit

Average Viz:

80 feet (St. Vincent); 100-plus feet (Grenadines)

When to Go:

Year-round

Flights:

SVG’s international E.T. Joshua Airport (SVD) is near Kingstown. Major gateways are Barbados, Trinidad and Puerto Rico.

For More: www.sportdiver.com/svg._

TRAINING

Underwater Naturalist: Learn more about the rich aquatic ecosystem in SVG by identifying major aquatic life groupings and interactions. Learn about the role of plants and predator/prey relationships as well. Go to padi.com._

DIVE OPERATORS Dive Bequia

The only PADI Five Star Dive Resort in the Grenadines, Dive Bequia has been in business for 27 years. Contact:

divebequia.com._

Indigo Dive

Located in St. Vincent’s Buccament Bay Hotel and Resort, Indigo Dive offers a handful of sites just a few minutes away. Contact:

indigodive.com.com._

Canouan Scuba Center

On the leeward side of Canouan, this PADI Dive Resort offers dive instruction to Divemaster. Contact:

canouandivecenter.com._

Dive St. Vincent

Groups of six get their own dive boat at Dive St. Vincent, the first operator on the island. Contact:

divestvincent.com._