It takes 10 minutes to get the allure of stand-up paddleboarding – 10 minutes to fumble down the edge of Southwest Caye, quads burning, and turn into a placid lagoon flanked by mangroves and sheltered from the easterly trade winds that blow across Glover's Reef.

Guide Cedric (Budge) Casimiro points out a sun-bleached iguana, eyeing us lazily from a branch above. Another vibrant world awaits below our feet, so we drop the boards, strap on masks and slip into the lagoon. There are sea grasses, anemone, sea urchins, conch shells, an orange starfish covered in knobby cleats. Spotted rays, surgeonfish, yellow goatfish, scrawled cowfish, grunts and sergeant-majors, their yellow bodies decorated with five black bars.

On the lagoon floor is a large bed of upside-down jellyfish, throbbing blotches of army green, mustard yellow, rust red and indigo blue. Their arms are clustered on top of their bodies (not on the bottom, like most jellyfish), where they attract growths of symbiotic algae. Their antennae drift like tethered tadpoles, each with a shock of colour and constantly pulsing as we drift above in barely a metre of water. It's like snorkelling through open-heart surgery.

"That's what I'm talking about!" says Casimiro, 37, his dreads glistening in the morning sun as we emerge from the lagoon. His students nod with new-found appreciation. Paddleboarding isn't just about strokes, turns and exercise – it's about low-impact access to a unique place like Glover's Reef, Belize.

And it is unique: Glover's is a coral atoll, one of just four in the Caribbean. The ring-shaped reef shelters delicate sea life, coral formations and sandy cayes. Seventeen of us have come from all over North America to camp in wood-floored safari tents, forgo most modern conveniences and tread as lightly as possible.

The camp, run by Canadian-based travel company Island Expeditions, is on the tip of Southwest Caye. Our little point has just enough room for 12 guest tents, four compost toilets, two cold-water showers, a kitchen and a dining hall. A hundred metres east, the open Caribbean crashes into the forereef, stacking coral and debris into a long barrier that keeps our side mostly calm – ideal for paddling expeditions to interior lagoons, patch reefs and coral heads.

Depending on our interests and the day's conditions, we sign up for combinations of stand-up paddleboarding (universally known as SUP), kayaking, sailing, snorkelling, conch diving, hand-line fishing or "hammock surfing." All activities (except the hammock) include steering and tips from experienced Belizean and international guides, which makes the reef accessible for novice and veteran paddlers alike.

Our group ranges from complete newbs to weekend warriors and an aspiring bayou guide. Some are in our 20s and some are in our 60s. Many are women, several are travelling solo and a few are return visitors. Almost none of us are exceptionally fit – the only real requirement is to enjoy jumping in the water and giving things a try. But it does help to be willing to rough it a little.

Each morning, a conch shell blows and we assemble in the dining hall for coffee, breakfast and a weather report. Our first morning, 32-year-old guide Mike Leslie briefs us on the reef's geography and heritage.

Glover's is a tall ellipsis in shape, 30 by 12 kilometres – about the size of Winnipeg. It contains more than 700 patch reefs and four cayes, one of which is home to a research station and a government fishery office. It's administered as part of the Belize Barrier Reef, the world's second-largest barrier reef and a UNESCO World Heritage Site; Belize has just enacted a moratorium on oil and gas exploration to protect it.

And the name? It originated with 17th-century English pirate John Glover, who was less interested in marine ecology than Spanish merchant ships. "Guys, if you find any treasure out there, just let me know where it is and I'll be sure to give you a cut," Leslie says with a laugh.

After a short introduction to the kayaks, we paddle out 10 minutes to a patch reef, tie up together and jump into the bluest water possible. We circle the reef for an hour with Casimiro, who delights in pointing out coral formations (brain, finger, tube, lettuce) and all manner of sea life (blue tang, blue chromis, damselfish, pufferfish, angelfish, parrotfish, lady of the sea, Caribbean squid, butterfly fish, southern stingray, lobster).

Our eyes are bulging, but so are our calves, which aren't yet broken in for all this swimming. Several of us pause to stretch them out before climbing into the kayaks and heading back for a lunch break.

The break is appreciated: A drift snorkel over the forereef awaits in the afternoon, followed by happy hour and a long, social dinner before the power goes off at 10. The next day, we'll kayak to Middle Caye, hunt hermit crabs on a sandbar, explore the research station, snorkel with trumpetfish, explore a brain coral the size of a small car and sail the boats home. The next, we'll take SUP lessons and harvest conch from a sandy lagoon surrounded by coral heads.

On it goes for five days and nights, a blur of paddling, snorkelling, fish spotting – and eating. All this activity is fuelled by the efforts of cooks Cynthia Andrew, 56, and Freddie Pau, 27.

They bring out pancakes, sausages, eggs, potatoes, tortillas, tostadas, fish in coconut sauce, grilled meats, carrot slaw, cauliflower salad, potato-corn chowder, chickpea curry, spinach salad, ginger cookies, cheesecakes, flan, fresh juices and an array of appetizers, all made from scratch in a rustic 250-square-foot kitchen shack that bursts with pots, knives, blenders, fruits, vegetables, spices and giant plastic bins of flour.

On one of our last evenings, Andrew and Pau revamp their menu on the fly to incorporate a large barracuda caught in a hand-fishing excursion. While the fish is prepared, Leslie and Casimiro organize a nighttime snorkelling expedition, which means postponing happy hour. "After a couple of rums, fish this big start looking like this," Leslie warns, widening his hands for comic effect.

So instead of mixing drinks, we plunge into the ocean with flashlights to mix with eels, yellow rays and a pair of mating crabs, which shrink back into the seagrass as we gather around to watch. Seeing this dark world brings a shiver of excitement – we're still chattering about it after drying off and reassembling. But the guides are less impressed.

"Sixty out of 100," Casimiro proclaims. "When we dive off Tobacco Caye [closer to the coast], we see six times as many lobster, rays, fish, even octopus."

As that sinks in, the conch horn blows for dinner. With grins and overdue cocktails, we climb the stairs to the dining hall to cap another day of privileged access to a unique place – and contemplate what tomorrow's "60" might bring.

Underground adventures

William Pleytes was 17, rambling with his dog, when he stumbled upon a Mayan cave on his family's farm in 1989. The discovery changed his life – but not until after a road finally reached the property in 1994, allowing him to begin guiding the cave, known as Che Chem Ha.

It still takes almost 45 minutes of potholed driving and cow-dodging, plus an uphill jungle trek of the same duration, to reach Che Chem Ha from the tourist hub of San Ignacio. But the journey is quickly forgotten as we descend into the cave, which the Mayans considered a gateway to the afterlife.

Pleytes outfits us with helmets and headlamps, whereas the Mayans squeezed through the narrow clefts with burning torches and offerings to collect holy water from stalactites. Archeologists are still studying the pottery, motifs and artifacts they left behind, more than a millennium after the cave was abandoned.

San Ignacio is also a base for trips to Mayan sites such as Cahal Pech, Caracol and Xunantunich, a ceremonial temple where two dozen smaller ruins are splayed around a central tower known as the Castillo. Rising 40 metres from a high point above the central plaza, the Castillo remains one of the tallest buildings in Belize. A climb to its top reveals broad views of the Guatemalan town of Melchor de Mencos and a valley that was farmed by 10,000 people, even after Xunantunich was abandoned amid earthquakes and political turmoil.

These Mayan sites were part of a connected network of palaces, temples and elevated highways that stretched across modern-day Central America. Weeks before our visit, researchers announced the discovery of thousands of ruins just across the Guatemalan border, the fruit of newly applied laser technology that allows them to see through jungle canopy to analyze stone structures and landforms beneath.

Your turn

Island Expeditions offers itineraries of two to 10 days in Belize. The Glover's Reef and Mayan caves trip costs $2,199, which includes all accommodations, taxes, fees and most meals but not air travel or gratuities (islandexpeditions.com).

WestJet flies direct from Toronto to Belize City, and several international airlines connect Canadian cities through U.S. hubs such as Houston, Atlanta and Miami. Belizean carriers Maya Island Air and Tropic Air link Belize City's international airport to the coastal city of Dangriga, reducing a two-hour drive to a 15-minute puddle hop.

The writer was a guest of Island Expeditions. It did not review or approve this article.