I recall my second dive quite clearly. It was at a place called Dorothea, in North Wales, a limestone quarry with a maximum depth of just over a hundred metres. Along with my buddy/instructor, we finned way from the safety of the ledge, and I stared down into the chilly waters that shifted from green to turquoise to dark blue to black. We went far deeper than we should have that day, down to thirty-two metres on what was a very early dive for me. Afterwards, watching my reaction, he said I’d probably end up a depth junkie. He wasn’t wrong.

But I became an instructor, and safety was first when I was training anyone. Nevertheless, I was, and still am, fascinated by deep water. Below thirty metres you feel completely cut off from everything landside, you really are in another world. It helps if the visibility is good. I’ve been down at fifty metres yet able to see dive boats on the surface. And sometimes you can find massive schools of fish swirling in the depths, such as tuna, as I found in Sulawesi, or even schools of hammerhead sharks, as I encountered on my deepest dive ever to seventy-six metres in Sipadan, off the coast of Borneo. And some wrecks are pretty deep, such as the scuttled German fleet in the area known as Scapa Flow in the Orkneys at the tip of Scotland.

But with depth comes danger. Nitrogen narcosis below thirty, the bends if you come up too fast, and oxygen poisoning at around sixty-six metres if diving on air, hence the title of the first book in the Nadia Laksheva series. I did black out at sixty-four during a (successful) rescue attempt in a Norwegian fjord. I didn’t expect to wake up again. And after a week’s deep diving in Palau in the middle of the Pacific, and then flying on to Phuket in Thailand, I had strong symptoms of the bends, tingling in all my limbs that wouldn’t go away. Being unable to communicate with anyone in the crummy hotel where I was staying (divers spend all their money on decent dive kit), and having heard that the nearest decompression chamber had just been relocated back to Bangkok, I assumed the worst and wrote a letter to my girlfriend, in case I didn’t wake up, or woke up paralyzed. These days I restrict myself to the thirty-to-fifty metre range, either for wreck diving or for big fish.

But I can always send the characters in my books deeper. 

In Sixty-Six Metres, that’s as deep as they go, and frankly speaking, it’s deep enough. In the sequel, 37 Hours, they don’t dive so deep, but sharks are the problem. But in the third volume, 88 North, due out 14th December, they go way deeper, diving on mixed gases, and even deeper via a submarine. I’m writing these scenes at the moment, and having a great time, since I doubt I’ll ever get to go as deep. It’s not all made-up, either. I used to know divers who worked beneath offshore oil rigs (of which I’ve been on a few), and these rigs feature in the third book. Those commercial divers told me some hair-raising stories, some of which have made it into the novel. 

But as divers, we have to be careful. I was trained by the British Sub Aqua Club (BSAC), and they have a saying. There are bold divers, and there are old divers, but there are no old bold divers. Still, when I’m down at depth in Mauritius on Tuna Wall at fifty metres with my buddy James, and I look down towards sixty or seventy, maybe seeing sharks or tuna near the bottom, I feel the depth beckoning.

Just one more reason divers never dive alone.