Zima Anderson suffered a horrific accident during a tough challenge on SAS Australia.

On Tuesday night's episode, the Neighbours star was tasked with jumping from a high platform and into the ocean with a Bergen bag.

But the actress, 25, slipped and fell from the great height, landing on the concrete slab beneath the platform.

The moment wasn't captured on camera, but viewers could hear the impact and Zima's painful cries.

As SAS Chief Instructor Ant Middleton rushed to Zima's aid and supported her head in case of any injury, emergency service sirens wailed in the background.

'This doesn't matter anymore. The exercise doesn't matter,' Ant assured her.

'That doesn't matter. You matter.'

Medical staff gave the soap star a green whistle for pain relief, as a defeated Zima shared her disappointment for not completing the challenge.

'I swear I was gonna be a good SAS recruit,' she said in a daze.

'You are! You are a good SAS recruit,' the DS team all replied.

The challenge was cancelled, with Zima getting carried out on a stretcher and taken to hospital.

She withdrew from the show on medical grounds with a fractured right elbow and wrist.

Speaking to the camera, Ant explained the show's challenges are designed to be 'as real as possible' and that in real life, 'accidents happen all the time'.

'We have to make sure that you can deal with those risks and that when it comes to real life training, you are capable and aware of having your own life in your hands,' he said.

Elsewhere in Tuesday's episode, The remaining SAS Australia recruits became extremely vulnerable when they were instructed to write down their most shameful secrets and read them the rest of the group during Tuesday night's episode of the show. 

Former diver Matthew Mitcham, 35, confessed to lying in his marriage to his husband Luke Rutherford, and admitted the problem might be compulsive.

'I've caused so much hurt and serious damage to the relationship. I hurt the people who are most important to me because honesty is not one of my core values. And I'm a liar,' Mitcham said.

'I struggle to tell the truth when it's difficult.'

Mitcham was later brought to SAS Australia Chief Instructor Ant Middleton for an interrogation about his dishonesty, where he made a shocking confession about his sexual behaviour outside his marriage.

Middleton asked Mitcham about the latest lie he told, and he admitted that he lies to his husband about sex with other partners even though the couple 'have an understanding.'

'Are you worried that you could be a compulsive liar?' asked Middleton.

'Maybe, yeah that would a very shameful thing for me to admit,' Matthew replied.