This one starts with a visit to an old friend in Puerto Vallarta. Someone I’ve known for decades, although for the last 10 years, since his emigration to Mexico, we’ve seen one another infrequently.

The visit began with some tension in that way meetings between old friends can be tense until you work out one another’s quirks — many of which become pronounced as we grow older. However, by the day in question, the relentless sun and our shared history had melted any discord and we were both enjoying ourselves so much that we decided to say yes when his generous friend offered us a daylong cruise on a 60-foot sailing schooner.

The morning was cool and clear as we boarded the boat. Our three-man crew was friendly and professional. The guide, Benjamin, was a bird and marine expert and a knowledgeable environmentalist.

We hugged the coastline for the first part of the trip, the sun getting warmer, but the breeze of the boat and the ocean around us rendered it bearable. Benjamin saw a circular rippling in the water that indicated feeding dolphins. The motor was cut and we glided in for a closer look. For a short time there was nothing, then suddenly they were breaking through the water near the front of the boat. Sinuous backs, sharp dorsal fins, fluked tails; a mother and calf and a larger one playfully raced under the bow and then they were gone.

We reached a lagoon of one of the Marieta Islands, a protected habitat said to have some of the best snorkelling in the world. Being a weak swimmer I entered the water somewhat nervously, but Benjamin was so reassuring and clear in his instruction that I was snorkelling as happily as my more experienced friends in a short time.

Treading water, my friend pulled his snorkel out of his mouth and said, “I feel like an extra in The Little Mermaid” as schools of king angelfish, black with neon-coloured stripes, came so close we could touch them. Benjamin dove gracefully to the bottom, overturning rocks to shoo out an octopus or to point out an almost invisible lobster. Then he led us through a mostly submerged archway, cautioning us to stay in the middle of the channel because colliding with the rocks can be very painful.

We emerged into one of the most magical places I have ever experienced. It’s called The Beach in a Cave, or Honeymooner’s Beach, depending on whom you speak to. There’s a popular image of this place circulating on Facebook. It shows clear blue-green water lapping against a pure white-sand beach surrounded by most of a tall volcanic dome that lacks a ceiling, making the entire place feel like the planet’s most secret cathedral to the elements.

To add a little danger to the wonder, our guide took us back into the water, sans snorkelling gear, and led us into another water-filled tunnel. It led to a larger cave with a number of openings to the ocean that allow the water to crash in, eddying around us as we carefully made our way across large, mossy rocks toward an opening in the opposite wall. Real dexterity and care were required. My friend said, “One slip and we’d be sliced to ribbons.”

His friend said, “I’m too fucking old for this.”

Later, on the return trip, after a hearty lunch, we lapsed into a contented silence, each of us dozing, lounging or silently regarding the amazingly complex topography of the water meeting air and light.

The next day, after the previous evening of laughs, Scrabble and a bit too much bourbon, my friend and I were having lunch when he told me the worst news a friend could possibly tell another. He’s been faced with a medical choice that involves either profound disfiguration or death. He’s never been the type to give up his looks and he’s never had any real desire to grow old. It was probably the last lunch we’ll ever share.

I was stunned. The many comments and questions I wanted to ask collided with a powerful surge of emotion. All I could muster was, “Thanks for yesterday.” He nodded and said, “It was perfect.”

And it was. It was the perfect day.