When it comes to the ocean, nothing terrifies Joe Knight. A professional free diver and off-shore survival trainer, he coaches some of Australia's most elite surfers, divers and water photographers to feel calm in the most treacherous of conditions.

Knight travels the world for free dive competitions and training programs and also holds watermanship workshops for surfers and the public near his home on the New South Wales north coast. (ABC : Margaret Burin )

Static apnea training and other breath-hold techniques are key parts of Joe Knight's free dive and water survival training. (ABC : Margaret Burin )

A professional free diver and paramedic, Joe Knight trains people to feel at ease in the ocean. (ABC: Margaret Burin )

Whether it is in huge pounding surf, or diving to depths where the light penetrating the ocean surface can no longer be seen, Joe Knight could not feel more comfortable in the water.

He started spear-fishing as a boy, and from the age of 18 turned free diving into career when he began working in the Navy as a clearance diver and paramedic.

Free diving is the ability to dive or stay underwater without breathing equipment.

Reaching depths of 171 feet (52m), he can hold his breath at ease for up to five minutes and 45 seconds.

"I came up feeling very fresh and comfortable and the experience in me wasn't painful at all, and that's the way I like to keep it," he said.

"For a free diver, that isn't long. Some of my friends are holding their breath for seven and eight minutes."

The 32-year-old's career has since evolved into training helicopter pilots and military personnel in off-shore survival, and off-shore rig workers in diving.

He also travels the world as an emergency stand-by at free dive events.

At times he is reminded about the incredible risks involved in his work.

Last year tragedy struck while he was working on the safety team at Vertical Blue, an international free dive competition at Dean's Blue Hole in the Bahamas, which at 663 feet (202m) is considered the world's deepest seawater sinkhole.

Knight had to lift US competitor Nicholas Mevoli out of the water after he lost consciousness at the surface, but he could not be resuscitated.

Most professional free divers black-out at some point in their career.

But years of intense psychological and physical training - including apnea, or breath-hold training - have conditioned Knight to feel most calm while swimming towards the darkness.

"The mental state is one of tranquillity, a very peaceful mindset and clarity," he said.

"It's a discipline, you have to learn it over many years, and it's something your life ends up revolving around."

The art of watermanship

From his home near Brunswick Heads, on the New South Wales north coast, Joe Knight holds waterman courses - from basic to specialist - designed to give members of the public skills in swimming techniques, ocean survival and rescue.

Founder of One Ocean International, he has worked with surf photographers such as Russell Ord who is renowned for capturing some of the heaviest waves imaginable off the Western Australian coast, and the likes of Byron Bay pro surfer Garrett Parkes who is registered for upcoming courses.

But his workshops also target average people who are simply terrified of drowning.

His own near-death experiences at the hands of mother nature have helped to keep him humble.

"Once I was surfing at a place called Hat Head, I was pretty young, and I wasn't paying attention to the conditions and there was a front coming up from the south and the swell was increasing and I got sucked out," he said.

"The sea was getting bigger and I ended up swimming for about an hour trying to get back in and I got to the point where I couldn't swim anymore, so I ended up catching this big wave in, got pin-balled around the rocks and got stuck in a cave underwater, and cut all my arms and legs and got washed up onto the rocks - that was scary."

Nowadays, he says that scenario would not faze him.

His ethos of being a great waterman comes down to five key elements: strength, flexibility, oxygen consumption, depth awareness, and structure of the mind.

"Without structure of the mind all the other four elements of watermanship are useless," he said.

"Panic, irrational fear, unwanted disorientation will destroy a waterman."

One of the scenarios he often simulates is being dumped in huge surf and getting rag-dolled underwater.

Apnea training is a key part of his coaching, enabling people to hold their breath for several minutes at ease if required and understand how their body is reacting to it.

"Breath-hold causes fear and anxiety, so the ability to be able to hold your breath for long periods of time without having negative reactions is being a breath-hold practitioner."

An ultimate waterman, Joe Knight is a person who feels at home in the ocean regardless of what it throws at him.

His next challenge will be in March when he will head to Western Australia to train some of Australia's best big wave surfers, including Paul Paterson.