On most liveaboards, the first thing the crew does is line up divers to check C cards and insurance. But on Aqua Cat, there’s something more going on.

One after another, 15 divers sit down for a long tête-à-tête with a dive instructor. I sidle up closer, eavesdropping as crewmembers ­interview each one on what they hope to see and do this week in the Bahamas’ Exuma Cays. Sharks, turtles, rays, ­macro, walls, pinnacles, drifts, reefs, lobstering, ­snorkeling, ­fishing, island hopping, ­kayaking, beach time, rum time, iguanas, swimming pigs — it’s a waterman’s fantasy of ­every fun thing these islands can offer. Wow, I think. We’re ­gonna need a bigger boat.

Turns out, we don’t.

On our very first dive, at a sunny, shallow north Exumas site called ­Barracuda Shoals, we come on the healthiest patch reef I’ve seen in the ­Bahamas — or maybe the entire Caribbean and ­Atlantic — in years. We drop in on three or four sharks in a ­totally ­natural environment: no bait, no scent. They’re curious but wary, and don’t come close. Big southern stingrays hide half-buried in sand, where they seem to think we can’t see them — we quietly fin by and let them preserve their illusions. Even cooler are the hunting yellow rays doing vigorous, full-body shakes whenever they find an ­unlucky mollusk. They’re oblivious to us, even when divers get right down on the sand, a space also full of adorable yellowhead jawfish popping in and out of view. Big pompano cruise by in the middle distance, and a good-size horse-eye jack makes a beeline right to me. A perfect little dive, and a promising start.

Moving to our next site, the yacht weaves through a string of iron-shore keys that barely crest the surface — bane of navigation, they make clear why the ­Bahamas was a “wrackers’ paradise” in days of old. Aqua Cat’s state-of-the-art navigation ­systems mean we can forget all that and focus on the view, bright sun illuminating a sea layered in strips of blue — ­royal, ­cerulean, aquamarine — ­alternating to the horizon.

At the next site, Pillar Wall, we have our first taste of the verticality that makes the ­Bahamas famous in dive. The terrain we’re sailing over is magnificent, like finning through the Himalayas. Up on top, long slow-growing ­fingers of coral extend, ­vying through the eons in a race ­always run and never won. It’s nature on a scale that ­exceeds comprehension. It’s humbling, and inspiring.

Rosy Toes Brigade

“Anybody get bit?” first mate Jason Russell-Smith hollers from the dive deck as 28-foot Sea Dog pulls along Aqua Cat’s port side to disembark us from a quick run over to Allen’s Cay. He’s not talking about sharks, although we’re seeing Caribbean reefies on every dive, and will see dozens at a feed early in the week where a chumsicle is suspended over the Austin Smith wreck for nearly an hour.

He’s talking about Bahamian rock iguanas. Their poor eyesight means they can mistake painted toenails for the biologist-approved grapes we’ve been feeding them. They’re hilarious, taking the fruit with a lightning speed that belies their ­lumbering waddle.

Sea Dog sets Aqua Cat apart from other liveaboards, and makes it a good option for groups with nondivers, something few dive yachts can claim. It’s a “nondiving activity” jet boat that ­ferries guests to places where they can freedive for lobster, tour a mangrove, or go birding, tubing, snorkeling or ­fishing, or just laze on a ­deserted beach, with or without an adult ­beverage in hand.

While Aqua Cat typically ­offers four to five dives a day, “Sea Dog caters to those who aren’t so hardcore,” says Aqua Cat’s South African captain, Des Greyling, 39, who’s been with the company since he started as a dive instructor in 2005. “If you’re out for adventure or just a rum punch and a towel, it’s all-encompassing.”

Sea Dog is dwarfed by ­102-foot Aqua Cat, a spacious, stable catamaran with a 35-foot beam that boasts two generators and three reverse-osmosis machines. “We’re like a little city,” Greyling says, or a cruise ship for divers, right down to the intercom that keeps us up to date on dives, meals and an ever-­unfolding range of amusements. Aqua Cat’s top deck might be the favorite, based on how many divers are there day and night, catching rays between dives, enjoying a sunset cocktail at the open bar, or gaping at the Milky Way and counting shooting stars after dark. Hearty meals are served buffet style in the catamaran’s sunny, roomy salon; cabins also are unusually large for a liveaboard and feature mostly king or twin beds and ­picture windows — the only bunks are pull-downs to add an extra ­diver to a cabin.

Greyling offers ­other ­reasons for Aqua Cat’s ­enduring popularity. For one, its home port, Nassau, is easy to reach from anywhere “because of the proximity to the U.S. eastern seaboard,” he says. More than that, it’s the lure of the ­Exumas ­themselves. “The variety of ­diving is ­fantastic,” he says of terrain that allows Aqua Cat to cater to newbies and advanced ­divers, from deep walls to shallow ­coral, ­sandy ­bottoms, drift dives or a shark feed.

And it’s warm. “­Skinny-dip diving,” Bret Sleight, 53, calls it. The new diver from ­Asheville, North Carolina, is doing his AOW cert on the boat, mostly in boardshorts and a rash guard. “I was ­never cold all week,” he ­marvels, recalling his open water cert in an icy South Carolina ­reservoir.

Reader Rankings for the Best Liveaboards

Love of getting wet is a passion the crew shares. “I’m excited for a beautiful day and to have this as my dive!” says Gustavo Buratto, our exuberant Brazilian instructor, briefing us on a site called Dog Rocks. Greyling and all of Aqua Cat’s instructors have pegged this as a favorite.

With that introduction, it shouldn’t surprise that Dog Rocks rivals anything I’ve dived in Cozumel or ­Little Cayman, each renowned for spectacular walls. Right away we see sharks, Nassau grouper, stingrays and queen ­trigger, and we haven’t even left the mooring.

At the wall, about a ­minute away, we drop through an arched chute called the Church, for the way it filters the light “like stained glass,” Greyling says — it’s at once glorious and quietly moving. Emerging into the blue at 85 feet, I turn back to see black coral in ebony and green draping the exit like lacy curtains; a big Caribbean reef shark cruises past in limitless viz. Dangling from one clifftop is a rope sponge 60 feet long, with every other kind of sponge and marine life hanging off it, like a cathedral bell pull decorated for a royal wedding.

That afternoon, the mood changes when we do our first drift, through Wax Cut, a ­common type of Exumas ­diving that’s uncommonly fun.

The tidally dependent ride can be “really slow to really fast,” from 2 to 5 knots, instructor Jill Blanchette says. “Since we have a full moon, this might be pretty quick.”

That’s an understatement.

We plop off Aqua Cat en masse in a negative entry and — whee! — we’re off, ripping backward, forward and every which way over a shallow valley dotted with coral tableaux, each one its own little Busytown. Swept alongside you are nurse sharks, turtles, triggers, angels and cowfish in colors from chartreuse to lavender. It’s one of those dives where you’ll be grinning from ear to ear the whole time, like a 5-year-old on a kiddie coaster. “Again! Again!” we demand as we wait to clamber back aboard.

Now and Forever

“Anybody get bit?” we hear again as Sea Dog pulls alongside the mothership. It’s ­Russell-Smith, laughing, but this time it’s not iguanas — it’s the famous swimming pigs of Big Major Cay. They aren’t really nippy, just a little pushy when it comes to the apple slices we’ve brought. But today all are as docile as piglets.

During the week, we’ve passed nearly 100 miles from Nassau down through the Exuma Cays Land and Sea Park to Staniel Cay, home to Thunderball Grotto, a beautiful snorkel site made famous in what might be the worst Bond movie ever. The grotto pales a bit compared with Rocky ­Dundas, caverns we dive ­inside the park where an ancient elkhorn coral is surrounded by newly ­sprouted baby elkhorns, a rare and hopeful sight, and evidence of the long arm of protection.

Founded in 1959, the 176-square-mile park was the world’s first marine ­protected area, and is one of few no-take zones in the hemisphere. On an island walk at Warderick Wells, the park’s headquarters, Greyling regales us with tall tales of pirates who sheltered here. Whether there’s any truth in them is hard to say; not in doubt is the living testament of the beauty and health of sites within and near the park, compelling evidence of the power of conservation applied over nearly 60 years.

At one of those ­protected sites — Jeep Reef, “a little gem,” Greyling says — picturesque islands of coral are ­arranged on sugar-white sand scooped by the tides into hills and valleys so bright that on a sunny day, the encrusting, vase and rope ­sponges all ­appear lit from within, complemented by colorful fish life from angels to butters, porgies and parrots. ­Early on, a mellow, manta-size eagle ray — possibly pregnant — wings in, followed by two smaller ones, and a super-friendly green turtle that doesn’t scurry off. Words fail, except two: Again! Again!

Need to Know

When to Go: Aqua Cat offers ­year-round itineraries; most ­diving is in the Exumas chain, but wind and weather can shift diving to the foot of Eleuthera.

Dive Conditions: Water temps in summer and fall are ­typically in the 80s and high 70s; many divers skip an exposure suit altogether or opt for a skin or shorty. Water temps in ­winter are in the low 70s; a 5 mm fullsuit is recommended for ­repetitive diving. Some dive sites can be affected by tides and subject to current; that also can affect visibility, which typically ranges from 60 feet to limitless.

Operator: Aqua Cat is operated by All Star Liveaboards. The 102-foot aluminum-hulled catamaran has 11 cabins with private baths and AC control, capable of carrying up to 30 divers. All diving is from the mothership, complemented by a 28-foot jet boat for ­nondiving ­activities.

Price Tag: Starting at $2,195 per person double occupancy, the price does not ­include port fees, rentals, ­nitrox or gratuities.