Members of the public are being challenged to take on the gruelling Royal Marines Commando Challenge and raise money for charity.
The endurance course sees competitors crawl, run and swim through thick mud and past obstacles, while being overseen by serving Royal Marines.
Jonathan Ball, of the Royal Marines Charity, said: "It is a very rare opportunity for any civilian to get the chance to undertake the Royal Marines' own endurance training course...
"It's a unique way to get a small insight on what a Royal Marine goes through during their training. Of course when they undertake the endurance training course, they will also be wearing a pack weighing approximately 32lbs, but we don't make our entrants do that."
The course is one of four commando tests recruits have to undertake to earn their green beret and is inspired by the four core values they're tested on during 32 weeks of arduous training - courage, determination, unselfishness and cheerfulness.
The challenge, which takes place on the Royal Marines Endurance Course on Woodbury Common, Devon, is to be held next weekend, October 14-15.
It hit the headlines last year when it was taken on by Superman star Henry Cavill.
He said at the time: "It was great. It's very important to support this charity because a lot of people don't realise the hardship of serving.
"It's important to support those people [who are serving] because they're out there protecting us and there's a family supporting them from home."
The event has raised over £5 million for charity since starting out a quarter of a century ago.
£5 from each registration fee goes towards safeguarding Woodbury Common, where the event takes place.