JUBA, South Sudan - Close calls with crocodiles, a brutal civil war and even the death of a fellow traveler have not stopped a British man from pursuing his goal: walking the entire length of the Nile River.

The 4,250-mile journey along the world's longest river will take a year to complete. It will see the former British army captain pass through six countries.

After four months of trekking through Rwanda, Tanzania and Uganda, Levison Wood is now in South Sudan. That country has little in the way of roads, bridges or electricity and has been weakened by a 4-month-long civil war.

The 31-year-old Wood said it took three years to plan the walk from Rwanda to Egypt. The White Nile starts in Rwanda and goes through Tanzania, Uganda and South Sudan. At Khartoum in Sudan, the White Nile joins the Blue Nile, which starts in Ethiopia. The Nile then flows through Egypt to the Mediterranean Sea.

"The Biggest Expedition"

"I've always had a passion for Africa since I was young. The River Nile has always interested me and I thought, what's the biggest expedition I could ever think of? And walking the Nile it was," he said.

Wood faces many dangers on the walk from both man and beast. Still, he noted, past explorers had it even worse - unlike him, they didn't have the luxury of a satellite phone or Google maps.

"We've had some close calls with buffalo, elephants and a very close call with a crocodile in Murchison Falls," a national park in Uganda, he said Thursday. The "toughest challenge," though, is keeping up the pace and not getting "too dismayed when there are delays."

On average Wood walks 20 miles a day, but he is seldom alone. His guide from Congo, who goes by the name Boston, has been a long-time companion. In South Sudan, three machine gun-carrying soldiers provide protection, while another South Sudanese man on a bike carries supplies.

"South Sudan has been a challenge to say the least," Wood said. "And when I set off on Nov. 25 I obviously didn't predict a civil war kicking off mid-December."

Serious Safety Concerns

Further complicating matters is the camera crew following Wood, who are there to shoot a four-part documentary series for U.K. and U.S. television. In America, the series will air on Animal Planet. Wood and his crew were arrested while filming near the only bridge that crosses the Nile in South Sudan.

Weaving through the chaotic traffic in Juba, South Sudan's capital, Wood and his crew set a rapid pace. Their South Sudanese guide occasionally barks orders to stop filming near a national memorial or military site.

There are serious safety concerns for this part of the trip: The Nile passes through Jonglei, a region of South Sudan that has seen heavy fighting in recent months.

"As that's the front line, I'll have to make a decision when I get there whether I have to move away from the river," he said.

Just then, a well-known Juba curiosity strolls past: a man who is totally naked.

The team laughs. "No comment," Wood says to his cameraman.

A Death In Uganda

While South Sudan appears to be the toughest part of his trip, it was in Uganda where terrible misfortune struck. Experienced American adventure journalist Matt Power, who was walking with Wood, died from heat exhaustion on March 10. Wood said the death forced him to reconsider his plans.

"We took a week off" to mourn Power's death and to "have a think about, 'Is this something we really want to be doing?,'" he said.

After speaking with Power's wife and family, Wood, with their blessing, decided to continue his trip.

"It is one of those things that really brings home" the fact that "this is not an easy thing to do. It's incredibly difficult and dangerous in parts, and all I can do is be as prepared as I can be and hope the same doesn't happen to me," he said.