A trail runner attempting to cross almost 500 kilometres of South Australia's roughest terrain faced his biggest challenge on a remote beach, but it had nothing to do with running.

Key points: Trail runner attempting to set a record on a tough SA track spotted stricken animal

Trail runner attempting to set a record on a tough SA track spotted stricken animal Wading out, he realised it was a dolphin floundering in shallow water

Wading out, he realised it was a dolphin floundering in shallow water He 'shovelled' the dolphin out to sea, but failed in record attempt due to partner's injury

Alan Clarke and Quentin Van Der Werf had set off to run the 'Walk the Yorke' trail — 478km of cross-country trails stretching from Port Wakefield to Moonta Bay on South Australia's Yorke Peninsula.

The pair were aiming to be the first people to run the journey unsupported, hoping to complete the trail in a week and set the fastest time for the route in the process.

Their hopes were dashed when a knee injury forced Mr Van Der Werf to step away from the run and support Mr Clarke, who finished the journey this week.

Mr Clarke finished a total of 517 kilometres in 8 days, 11 hours and 38 minutes and will look to claim the fastest known time for a supported runner on the track.

But neither could have been prepared for what they saw sitting still in the shallows of a remote beach.

Curiosity leads to discovery

Mr Clarke said he had started out early and was just beginning to pick up his stride when he looked out and saw something in the water.

"I was going along Hardwicke Bay and I was about 20km into the day and I saw an animal out in the ocean, maybe a seal or a shark someone had caught the night before — or it might a dolphin," Mr Clake said.

"I took my shoes and socks off and waded out and sure enough it was a dolphin.

The trail showcases some of Yorke Peninsula's most rugged coastlines. ( Supplied: In The Flinders )

"It seemed happy enough, apart from being beached … I knew time was a bit of a factor so I just did my thing."

Mr Clarke then proceeded to grapple with the task of moving the dolphin back out to deeper waters, having already completed 380km of his journey.

He said the animal was about two metres long and weighed about 100 kilograms.

"In the end I ended up hugging him and shovelling him out to sea," he said.

"I asked him when I got to him whether he was going to swim off when I got him out to deeper water … when I got him out there he just went".

The dolphin had beached itself in Hardwicke Bay on Yorke Peninsula. ( Supplied: In The Flinders )

Dolphin rescue a highlight of massive adventure

Mr Clarke said the experience was just another moment that proved the extreme adventure was worth it.

Alan Clarke spoke with the ABC from a wombat burrow to protect himself from a dust storm. ( Supplied: Alan Clarke )

"I'm doing it for stuff exactly like this, the stuff you get to see out here is amazing," he told ABC North and West's Angela Smallacombe.

"I'm currently in a wombat burrow in the middle of a dust storm, it is a new one for me.

"It's been an almost transcendental experience at times."

Messrs Clarke and Van Der Werf operate a trail running business in the Flinders Ranges, but wanted to push themselves further.

"I had my 40th birthday not long ago and I wanted to achieve something off my bucket list," Mr Clarke told ABC Eyre Peninsula's Emma Pedler before beginning the trail last week.

"I think it's a good journey of discovery."

The 'Walk the Yorke' trails cover many different terrains including remote beaches. ( Supplied: In The Flinders )

Mr Van Der Werf was hoping to lead by example.

"I wanted to test my limits of endurance and set a good example for my kids to prove anything is possible," he said.

The duo had set off with as many supplies as they could on their backs but Mr Clarke admitted it was not an easy task.