Stranded Auckland mountain bikers rescued near Tarawera Falls after cold and damp night

Laurence Kerby (left) and Grace Anderson were rescued by police after a mountain bike trip went wrong. Photo / Ben Fraser

Two mountain bikers stranded in a forest overnight after a disastrous trail ride say they did their best "Bear Grylls" impersonation - huddling under large ferns in chilly conditions - as they waited for daylight to break.

Laurence Kerby and Grace Anderson from Auckland ran into trouble on their 90km bike ride on Sunday in the Lake Tarawera area after the track turned out to be too rough and rocky for bikes.

They were prepared for tough conditions, but unfortunately they went "too hard" taking photos or videos on Snapchat at the start of their trip and their phones went flat quicker than expected.

Their back-up plan was to charge them with a power bank, but it was the one important piece of equipment they'd forgotten to throw in the backpacks.

The 23-year-old flatmates ended up spending 15 hours waiting in the bush between Rotorua and Rerewhakaaitu until rescuers found them.

Kerby and Anderson said they were told by a local the 90km trek could be completed on mountain bikes.

However, 20km in, Anderson's shoe - which clips into her bike's pedal - broke and they had to spend time using a bungee chord to put it back together.

They struck more difficultly on the track as parts couldn't be cycled across.

"We ended up hauling our mountain bikes along the side of the river and it was rocky and steep," Kerby said.

Then Anderson's other shoe broke and she was forced to trek and bike the rest in socks and slides.

By 8pm, when it was dark and they were only about 30km in, they decided to use what little phone battery they had left to call Kerby's father and let him know they weren't going to make it to their accommodation and they would sleep the night in the bush.

Kerby's father alerted Anderson's mother, who called the police.

The riders were feeling pretty good and had torchlight so they decided to keep trekking to see how far they could get in the dark.

By just before midnight they were only 45km in and, little did they know, slightly off track.

Three of their four torchlights had died and the final one was on its last bit of battery power.

"The terrain was getting rockier and steeper and at 11.55pm we thought we'd better stop."

Kerby said they then did their "Bear Grylls" impersonation (Man Vs. Wild) and made a tent out of ferns.

Despite their spirits being relatively okay until this point, the night was a different story.

Anderson said she would ask Kerby every half an hour what the time was as neither of them slept for any longer than 10 minutes.

"We were huddled up next to each other trying to keep warm ... It was so cold and it took so long."

By 5.45am they were feeling tired, cold and wet so they decided to set off their Personal Locator Beacon, which alerts the Rescue Co-ordination Centre New Zealand.

Senior Constable John Fredericksen said a couple of Search and Rescue officers had already spent Sunday night until 11pm looking for the pair.

Laurence Kerby (back left) and Grace Anderson were pleased to see the Police Search and Rescue team, including Constable Kennedy Wilson. Photo / Supplied

The damp, overcast and foggy conditions yesterday morning meant Police Search and Rescue weren't able to put a helicopter in the air to find the pair and instead a ground crew of four searchers walked into the bush, finding them not far from Tarawera Falls about 10.30am.

Fredericksen said Anderson's mother had given them good information about the equipment they had on board and the couple were lucky to be fit and healthy.

Kerby and Anderson said they felt confident they could have made it out themselves but were happy to see the rescue team.

They said the experience had not put them off future rides, but next time they would choose a shorter track- and would triple-check the power bank was packed.