A 65-year-old Lithuanian man who had his left leg amputated at the knee during a rescue operation near Tasmania's remote south-west remains in a critical condition.

The man, whose identity has not been disclosed, was part of an international group of 11 people embarking on a multi-day pack-rafting trip along Tasmania's remote Franklin River.

Police said they believed the man's leg became trapped in a rock crevice on Friday afternoon while he was "scouting" the area on foot along the Franklin River's banks.

He used a GPS-enabled device to call for help but remained trapped and partially submerged in water from the waist down for about 20 hours.

Following several unsuccessful attempts to free the man, the decision was made by medical emergency crews to amputate his leg at the knee.

The man was airlifted from the site, south of Frenchmans Cap, to the Royal Hobart Hospital on Saturday.

Police confirmed the man's family had been contacted and the remaining 10 people in the group have also been airlifted from the river.

Rescue team describe 'worst-case scenario'

Ambulance Tasmania intensive care workers, flight paramedics and specialist retrieval doctors were winched to the site to treat the man.

Swift water rescue technician with Surf Life Saving Tasmania Ace Petrie was one of the first people at the scene, and was in the water for 14 hours with the man.

"To give you an idea where his entrapment was, his knee was approximately three-quarters of my arm length to get down, so we had to get equipment into that water that was quite fast-moving," he said.

The man spoke little English, which added to the complexities of the situation.

"We couldn't actually take his mind off the situation and talk to him about his family or, you know, his trips that he's done, so that was really hard," Mr Petrie said.

Intensive flight care paramedic Mitch Parkinson said the priorities included keeping the risk of hypothermia at bay.

"Our efforts were to keep him warm as best as possible, acknowledging that he's in a torrent of water, and to keep him fed and watered as much as we could," he said.

"Between some broken English, some hand signals and some requests, we were able to have his Lithuanian party continue to supply him with hot drinks delivered by thermos and hot meals."

Mr Parkinson said there were legal and ethical considerations to the "life or limb" discussion, which occurred through a Lithuanian translator.

"We benefited that one of his party was a doctor in Lithuania, and so where we provided our information in English as best we could, he was then able to convey as best he could," Mr Parkinson said.

"What I saw was an exceptionally strong and robust man that had maintained that through the night into the morning."

Tasmania Police Senior Constable Callum Herbert said it was a very complex rescue mission with risks posed to all involved.

"This is pretty much the worst-case scenario you could get, aside from drowning," he said.

"It was a very dynamic, changing, hazardous environment that there was a potential for injury or serious injury that could have occurred [to rescuers]."

'Specialist equipment' used in rescue mission

Police said the "complex" rescue mission involved an estimated 30 people across several different agencies.

These included Tasmania Police, State Emergency Service, Tasmanian Fire Service, Ambulance Tasmania and Surf Life Saving Tasmania.

A fixed-wing aircraft from the Australian Marine Safety Authority was also deployed to provide communication coverage, due to limited reception in the area.

Multiple attempts were made on Friday and Saturday to free the man using "specialist equipment", including a wilderness rescue tripod — called an "Arizona Vortex" — to attempt to manoeuvre the man from the rocks; swift water harness equipment; and Tasmania Fire Service equipment, including hydraulic cutters.

Ambulance Tasmanian intensive care workers, flight paramedics and specialist retrieval doctors were winched to the site to treat the man.

Mr Petrie said the team used ropes and pulleys to try to free the man before moving to hydraulic equipment.

"So people refer to them as the jaws of life, some spreading equipment, some airbag equipment and these have a capacity of 50 tonnes and we were not budging these rocks at all," Mr Petrie said.

Group was 'well-prepared'

Acting Assistant Commissioner Doug Oosterloo said the international group was "well-equipped and well-prepared" for a rafting trip, and the man was wearing a wet suit.

However, he said the significant amount of time in the water led to an increased risk of hypothermia.

Police said the man was kept warm and as comfortable as possible with extra clothes, hot food and drinks.

"Even if you are well prepared, even if you do take all necessary precautions, things can go wrong."

The group was on a global rafting tour, with Australia their last stop of five countries.