It’s hard not to panic when your oxygen supply is cut off. Warren De Klerk was diving in a Bermuda cave when his oxygen tank knocked against the ceiling, jarring a vital valve.

“I managed to stay calm,” said the 35-year-old. “For about 20 seconds I wasn’t getting any air.

“All I needed to do was reach around and put the valve back, but a short time before I’d fallen while snowboarding in France and banged myself up.

“I was very stiff and reaching around behind me wasn’t as easy as it sounded.”

He managed, with difficulty.

“When you’re cave diving, you either fix the problem and get out, or you die trying,” he said. “There’s no rescue squad to come and save you.

“It sure felt good when the oxygen started flowing again.”

The former chairman of the Bermuda Sub Aqua Club (BSAC) will discuss his diving adventures on Thursday at the Bermuda Underwater Exploration Institute. He’ll be joined by diver and photographer, Ron Lucas.

Mr De Klerk usually dives in the open ocean; even there he pushes the boundaries. His most dangerous dives in Bermuda were below 200ft. Most recreational diving is done between 100ft and 130ft, going deeper requires special training and equipment.

“It is like a whole different world when you go deeper,” he said. “You are seeing coral formations, and sea creatures that are very brightly coloured in unique shapes.

“But it is more dangerous because you have to take quite a lot of tanks with you with different gas mixes. There are things that can go wrong. On ascent you can run out of air, or if you ascend too fast you can injure your lungs or get decompression sickness.”

He enjoys taking photographs of his adventures to show family and friends.

“The largest living creature I have photographed underwater would be a very large sting ray that I saw in Sodwana, South Africa,” he said. “It was accompanied by a moray eel and a grouper. I wasn’t sure if they were hunting together or what, but I had to ascend and finish the dive so I only got to take one or two quick photos.”

Macro-photography, the art of taking shots of very small things, is one of his new passions. A Lembeh pygmy sea dragon he spotted diving in the Philippines is the smallest thing he’s captured so far.

“The guide was pointing at what looked like a very small twig,” he said. “It was moving but because it was so thin and moving around I had a hard time finding it. Then I had to get it in focus. It was the size of my pinky nail and well camouflaged.

“The challenges are firstly, finding a subject. If you are not diving in a place you are very familiar with then having a guide to help find the creatures is key.

“Secondly, to take a good photo you need a good angle on the subject. It can be tough.”

The South African uses an Olympus mirrorless camera with different lenses for macro photography. “We were pretty inland,” he said of his childhood in the Gauteng area. “But I always enjoyed any trip to the beach, to snorkel or swim.”

The accountant was determined to take up scuba diving when he moved to Bermuda in 2007. He learnt through the BSAC, and eventually became an instructor.

“As a volunteer with the BSAC I help people progress their diving skills,” he said. “I definitely get a sense of satisfaction in introducing new people to the ocean.

“I have trained people from all over the world. Some of my former students are now passing on their skills to others.”

Mr De Klerk and Mr Lucas will speak at 7.30pm. Tickets, $20 for members and $25 for non-members, are available on 294-0204 or at the BUEI gift shop.