Most divers travel to Cozumel for one reason: its reefs. Towering walls, crystal-clear water and effortless drift dives have made the Mexican island one of the Caribbean’s most celebrated diving destinations. For decades, divers have travelled here to glide along dramatic coral slopes, encounter huge turtles, eagle rays and swirling schools of reef fish, before ending the day convinced they have experienced the very best Cozumel has to offer.

But over the past few years, another kind of diving has been establishing itself beyond those famous reefs. This type of diving doesn’t take place above colourful coral formations or along spectacular drop-offs. There is no reef to navigate, no wall to follow and, for much of the dive, no visible bottom at all.

Instead, it begins several kilometres offshore, long after the sun has disappeared below the horizon. That is: blackwater diving. What surprised me most wasn’t that this entirely different style of diving had arrived in Cozumel; it was how quietly it had established itself. When I mentioned it to a local dive instructor who had even dived alongside Jacques-Yves Cousteau, he simply looked at me with a puzzled expression. “Blackwater?” he asked. He had never even heard of it. That conversation stayed with me throughout the day.

If someone with decades of experience diving around Cozumel didn’t know this existed, perhaps blackwater diving really was one of the island’s last genuine insider experiences? Yet blackwater diving wasn’t an experimental expedition or a one-off trip organised for underwater photographers. It had, slowly and modestly, become a regular part of Cozumel’s diving scene.