A British expat has been left with a broken leg and facial injuries after flouting warnings and jumping from an iconic waterfall in the Kakadu National Park south of Darwin.

Josh Jones, 25, broke his left leg in two places and sustained a dislocated knee and facial injuries when he plunged around 30 metres from a ledge at Jim Jim Falls on Saturday afternoon.

A group of good Samaritans, including a GP and three medical students, stretchered Mr Jones to safety. ( Supplied: Daniel Fitzgerald )

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"I saw the ledge and thought hey, that's possible to jump off," he told the ABC.

"It was just pure impact [when I hit the water]. I tried to pencil, it took the wind out of me, came up and the left leg didn't feel too good.

"I swam over to the edge, got a bit of air and … the left foot was out far to the left.

I thought yeah, that's got to be broken."

Fortunately for the newly-fledged Darwinite, who'd downed "about 10 beers", a GP and three medical students were visiting the falls when the incident occurred.

With a bit of ingenuity — and a pair of trusty jean shorts — the group of good Samaritans constructed a homemade stretcher and carried the former Yorkshire resident to safety.

"About eight people carried him out … it's about 900 metres or so, but you've got to go over these huge big boulders and there's no path there whatsoever," said Daniel Fitzgerald, who witnessed the incident and came to the expat's aid.

"He's lucky to survive … I thought he would hit the bottom of the cliff, and not the water."

Mr Jones, who said he was "gutted" by the turn of events, was taken to the Jabiru Clinic before being airlifted to the Royal Darwin Hospital in the early hours of Sunday morning.

"[I want to thank] all the guys who came to help me, four doctors and everything … strapped me up, pulled it [my leg] straight and we all got back to the camp," Mr Jones said.

"They made up a homemade sling, a stretcher … and dragged me all the way back for hours."

A Kakadu National Park spokesperson said visitors were encouraged to "follow safety directions, notices and warnings signs, and not to take unnecessary risks that may put you and others in danger".