Stranded couple rescued from Australian outback after writing "HELP" in mud

A quick-thinking Australian couple who scrawled the word "HELP" in the mud has been rescued from a crocodile-ridden part of the country's remote north after their vehicle got bogged on the marshland.

Shantelle Johnson, her partner Colen Nulgit and their puppy, Ace, were rescued by search teams at Barra Hole near Marralum on Monday afternoon after being missing for 26 hours, the Australian Broadcasting Corporation reported.

The couple lit spot fires and scratched "HELP" into the mud after their utility vehicle became bogged during a fishing trip to the Keep River National Park in the Northern Territory, close to the border with Western Australia.

The couple, from the East Kimberley town of Kununurra, spent Sunday night in their bogged car but got little sleep.

They had earlier spotted crocodile tracks and were worried about the tide bringing the reptiles close to the bank.

"We were stuck on the marshland and we were right next to saltwater," Nulgit said.

"We stayed in the car the first night and then we saw the water rising.

"We grabbed everything and took it about 20, 30 metres from the car," he said.

Luckily, the couple had informed the family where they were going and when to expect them back.

In their home town of Kununurra, 1.5 hours' drive away from the park, Johnson's mother called the police when they failed to return Sunday night.

On Monday, Kununurra police coordinated a search party using a plane from a local company to find the pair, the Western Australia Police Force said in a statement.

Nulgit said he and Johnson lit a fire as soon as they heard the plane to help draw attention.

They had very little food but had a carton of water bottles packed.

By the time the search team spotted the smoke from their fire and the sign in the mud, the pair was getting worried.

Nulgit said they had seen crocodile tracks in the area earlier and, as the waters rose and the sun set, became afraid of being swept away by a large tide -- or being attacked by crocodiles or dingos.

"These crocodiles that we get here, they're not afraid of humans, they're not afraid of anything," he told CNN.

"When they [the rescuers] came a bit lower to the ground, we jumped out of the car and started to wave them down.

Kununurra police praised the couple for staying with their vehicle and letting family know where they were going.

"It could have been a different story if they hadn't done that," Acting Sergeant Dean Andrzejaczek said.

"It's always a good idea to tell family where you're going and what time you are expected back," he said.

Nulgit said the adventure would not deter them from heading out again -- although next time they will have a recovery kit organised beforehand.

"I'm just grateful for everyone who pitched in and helped and came out to look for us," he said.

"We're pretty lucky surviving and getting out of that," he added.