A man narrowly avoided being hit in the head by a falling rock at Franz Josef Glacier and his partner suffered a broken foot after they jumped a barrier this morning.
Constable Bill Parker said the pair - a 34-year-old New Zealander and his 24-year-old Canadian girlfriend - read the warning signs, "but they thought they'd be alright so they climbed over the barrier".
They climbed down to where the river came out of the glacier terminal and were caught in a rock slide.
Mr Parker said a rock, slightly larger than a basketball, struck the woman on the foot, fracturing it and causing severe bruising and lacerations.
She was flown to Franz Josef then transferred to Grey Base Hospital in Greymouth.
The man was hit in the chest by a rock, receiving cuts and a bruised sternum.
Mr Parker said rock slides were a regular occurrence on the glacier and this served as another warning.
"I don't think it was a slide that would have buried them, but if the man had been a couple of inches back the rock would have smacked him in the skull and killed him. So it's just down to luck at the end of the day."
In January 2009 two Melbourne brothers were killed after ignoring warning signs on Fox Glacier to pose for pictures.
Ashish and Akshay Miranda were crushed by an icefall having stepped over a safety rope and waded through a stream to reach the glacier terminal.
In December the Department of Conservation told a coroner's enquiry its staff were powerless when tourists chose to endanger themselves.