(CNN) — The Atlantic Ocean off the southern-most tip of Africa is so cold it feels like your skin is burning. But still Craig Foster slips into the frigid water every day, without a wetsuit or scuba gear, off to explore an underwater kingdom.
Some might call him reckless -- in the past, Foster, a filmmaker, has dived with Nile crocodiles in Botswana's Okavango Delta and swum with great white sharks. But for the past eight years, he has turned his attention to a vast underwater kelp forest off the west coast of South Africa where he spends his days tracking sea creatures.
He has now published a book, along with fellow diver Ross Frylinck, documenting his close encounters with these wild animals.
The book, "Sea Change: Primal Joy and the art of underwater tracking," details how he touched a cat shark on its "nose" before it lay relaxed in his hands "tame as a puppy." It describes how an enormous stingray wrapped its wings around him for a few frightening seconds, and how a Cape clawless otter reached out to touch his face.
But his most memorable encounter was with an octopus he befriended and accompanied on hunts.
Foster said it took years of diving and learning how to completely relax around animals before they started engaging with him.
Sea Change Project
Foster's octopus even made a cameo on the BBC's "Blue Planet II" documentary last year, where it demonstrated an impressive camouflage technique in which it grabs shells and stones to build a temporary armored shell around itself to ward off small predators.
This is just one of dozens of never-seen-before behavioral traits that Foster has witnessed on his dives. He has discovered seven new species, including a shrimp that was named after him: Heteromysis Fosteri.
Dangers in the deep
Unsurprisingly, Foster doesn't fear the bigger beasts that patrol the sea forest.
"Certainly (it is scary) if you're not expecting it and a big white shark is there in front of you and the water is murky," he told CNN. "But to be honest there's very little to fear from the animals, they are not the danger."
Over the years Foster has taken thousands of intimate photos of wildlife, including this extreme close up of a pyjama catshark's eye.
Sea Change Project
Yet Foster has put his life on the line in the ocean.
"I've come very close to death a number of times, but never close to death from a shark," he said. "It's always being thrown by a huge wave onto a rock, being cut into pieces, or jammed in a cave underwater."
He is more mindful of the multiple threats facing the kelp forest: plastic and chemical pollution, over fishing, poaching, ocean mining and climate change.
Through his work Foster hopes to raise awareness of what he calls the "great African sea forest" — which spans from Cape Town up the coast to Namibia.
This particular kelp forest extends for 1,000 kilometers and is just 100 meters wide. It is one of the most productive ecosystems in the world, providing food, shelter and the ideal habitat for various species including endangered sea snails called abalone, the Cape fur seal and a variety of shark species.
Foster believes that if he can get others to think of this sea forest as one of the natural wonders of the world, much like the Great Barrier Reef, they will be inspired to conserve it.
Marine scientist Kerry Sink is leading the charge to protect South Africa's unique and threatened offshore marine life.
Protecting underwater worlds
But Foster also stressed the need for marine protected areas to further conserve South Africa's waters.
Last month, South Africa's Department of Environmental Affairs approved the declaration of 20 marine protected areas, collectively covering 50,000 square kilometers. This means 5% of the country's oceans are now protected, compared to 0.4% previously.
"We are now working to try get to 10%," said Foster. "I think marine protected areas are absolutely critical, we should ideally be at 50%."
He adds that it should be in everyone's interest to "honor our pact with the wild."
"Our African ancestors lived here for hundreds of thousands of years and left us with a completely intact ecosystem," he said. "It's our duty to do the same for our children."