JUBA: Close calls with crocodiles, a brutal civil war and even the death of a fellow traveler have not deterred a British man from attempting to walk the length of the Nile River.

The yearlong 4,250 mile journey along the world's longest river will see the former British army captain pass through seven countries.

After four months trekking through Rwanda, Tanzania and Uganda, Levison Wood is now in South Sudan, a country with little infrastructure that has been destabilized by four months of fighting between pro- and anti-government forces.

The 31-year-old said it took three years to plan the walk from Rwanda to Egypt.

''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 told The Associated Press.

Though he faces many dangers on the walk from both man and beast, Wood noted that past explorers didn't have the luxury of a satellite phone or Google maps.

''We've had some close calls with buffalo, elephants and very close call with a crocodile in Murchison Falls,'' a national park in Uganda, he said Thursday. '

'The toughest challenge I'm finding is to keep the momentum going and not get 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 AK-47 wielding soldiers from the commando battalion flank him as security. Another South Sudanese man on a bike ferries 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.''

Further complicating matters is the camera crew following Wood to shoot a four-part documentary series for UK and US audiences on Britain's Channel 4 and America's 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 blistering pace.

Their South Sudanese guide occasionally barks orders to stop filming near a national memorial or military installation.

There are safety concerns for this leg of the trip. The Nile passes through Jonglei state, a region 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.

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

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

While South Sudan appears to be the toughest part of his trip, it was in Uganda where tragedy struck.

Experienced American adventure journalist Matt Power, who was walking with Wood, died from heat exhaustion March 10. Wood said the death forced him to reconsider his plans.

''We took a week off just to contemplate what happened and 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.

''It is one of those things that really brings home the reality 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.