Everyone who visits Puerto Vallarta gets to know about the mysterious beach and wants to visit - although only a lucky few can.

Puerto Vallarta is a resort town on Mexico's Pacific coast, in Jalisco state.

It is known for its beaches, water sports and nightlife scene.

The cobblestone centre is home to the ornate Nuestra Señora de Guadalupe church, boutique shops and a range of restaurants and bars.

El Malecón is a beachside promenade with contemporary sculptures, as well as bars, lounges and nightclubs.

All of a sudden, all that was dark morphs into light.

We're swimming through the inky, narrow cave opening to Hidden Beach where the sun, in contrast, is shining gloriously, illuminating the tiny bay a sparkling aquamarine, the beach a golden brown and the sky a brilliant azure.

My son, Alex, my daughter, Grace, and Iare on the Snorkelling at Isla Marietas adventure (US$99 per person) organized by Ecotours de Mexico, an hour off the coast of Puerto Vallarta.

As we climb ashore we're breathless and exhilarated to be in this enchanted enclave.

Our eyes automatically gravitate skyward in an effort to figure out where we are, how we got here and why Hidden Beach is such a stunning, geological rarity.

A stunning, geological rarity

Hidden Beach is effectively mid-island, accessible only by the tapered cave we swam through.

The opening to the sky, an oculus, if you will, is a perfect oval formed when the roof of the cave, which was also part of the island's surface, collapsed sometime in the 1990s.

The resulting crater isn't the usual ruin associated with such a ground cavity because the uncovered beach and water below is so spectacular.

Once we have the geology figured out, Alex, Grace and I wander the beach, splash in the water, check out the antechamber caves and chatter about how lucky we are to have discovered this paradise.

Well, maybe 'discovered' is too rich a word.

Ecotours de Mexico

We wouldn't be here at all without Ecotours de Mexico and expedition leader Margarita Garcia.

Hidden Beach had become such a hot, international tourist destination that up to 2,500 people a day were showing up in all manner of boats, bumping into each other as they swam in and out and tramping the beach in a crowd.

The Mexican government stepped in 2016 and started limiting access to just 117 visitors a day to Hidden Beach.

More are allowed on Maietas' regular beaches and surrounding waters for snorkelling.

However, Hidden Beach is the hot ticket any only vetted tour operators can get permits for their guests to hit the crater.

That's why Ecotours de Mexico brings only 10 tourists a day to Marietas in a nimble Zodiac for the exclusive Hidden Beach excursion.

As an added bonus, our group also snorkelled, ran through the rock arches at La Nopalera Beach and enjoyed humpback whale and dolphin sightings on the way there and back.

My wife, Kerry, and I touted our two weeks in Nuevo Vallarta as the best-of-both-worlds.

Bahia del Sol Resort

Kerry found an ideally-located condominium for us on VRBO in Bahia del Sol Resort, where the view is all pool, palm trees, 10 kilometres of beach and the Pacific Ocean.

We had the first week to ourselves for long beach walks, cycling, lounging on the beach and poolside, wine at sunset and dinners at nearby authentic Mexican restaurants La Isla, Coco Beach and Riviera Grill.

www.bahiadelsol.com.mx

The second week our grown up kids joined us for the Hidden Island excursion, more beach and pool time, discovering Taco Cabana and Fajita Republic restaurants nearby and hitting the beach club and restaurant scene off Puerto Vallarta's famous Malecon.

Useful links

www.visitpuertovallarta.com