Two Northern Territory police officers have trekked almost 15 kilometres to get help after their vehicle washed off a crossing in a crocodile-inhabited river near Katherine.

The incident happened when the officers were travelling from Yarralin, 265km south-west of Katherine, to Lajamanu, late on Sunday.

A police spokeswoman said the officers were heading to the small town, which is home to fewer than 1,000 people, to relieve other police who had finished their shifts.

When they approached the Victoria River at Dashwood Crossing, having made the crossing before, they deemed it safe to cross.

But about 55 metres into the river crossing they ran into trouble and were forced to abandon their vehicle.

Neither of the officers were injured but they were forced to walk to Victoria River Downs Station to raise the alarm, almost 15km away.

Nobody else was in the vehicle at the time it was washed off the crossing.

Dashwood Crossing deemed impassable by authorities

The Victoria River is known for its saltwater crocodiles and last year a 3.75-metre specimen that had been hunting cattle was caught only 2kms from Dashwood Crossing.

Dashwood Crossing has now been labelled by authorities as impassable, and Pauline Haseldine from the Top Springs Pub Hotel, about 100kms away, said the Victoria River had been in flood in recent days with levels more than one-metre high.

She said the river was deemed impassable at heights above 30 centimetres.

But Ken Beresford who owns Katherine Towing said the police could not be blamed for the incident, which happened because part of the concrete causeway had washed away.

"Who would imagine the concrete would have washed away?" Mr Beresford said.

"They were the first ones across it [since the concrete had gone].

"It's no fault of the cops."

Policemen trekked to station barefoot

Mr Beresford said when his team got to the crossing the police had to get to the other side of the river to recover the keys and other possessions.

During the attempts to walk across the river one of the policemen was washed into the water five times before successfully returning, he said.

The two policemen who raised the alarm had walked the 14.5kms to Victorian River Downs Station barefoot, seemingly because they had been driving the car in thongs, Mr Beresford said.

"The car is a mess. It has a really massive gouge down the side."