A British tourist who died during an extreme sport excursion in New Zealand took the trip with a company ill-prepared for a rescue, a court in the country was told.

Emily Jordan, from Worcestershire, became trapped between rocks and drowned while "riverboarding" - riding a body board on fast-flowing rapids - in the Kawarau River Gorge near Queenstown on New Zealand's South Island.

Black Sheep Adventures Ltd, which trades as Mad Dog River Boarding, and company director Brad McLeod both face three charges under New Zealand's Health and Safety in Employment Act following the death of the 21-year-old on April 29 last year.

Miss Jordan's father Chris was in the Queenstown court yesterday as prosecutor Brent Stanaway told Judge Brian Callaghan that the operator had not taken all practicable steps to ensure the safety of its customers and employees.

Mr Stanaway said Miss Jordan's group was given a safety briefing about 12.30pm but was not told of the "significant and inherent hazard of entrapment".

"No mention was made ... that if they became entrapped their chance of survival was by no means guaranteed," the court heard.

The group entered the water about 500 metres upstream of a power station called Roaring Meg and negotiated one set of rapids before experiencing trouble at a second.

Mr Stanaway said: "Miss Jordan became entrapped directly against the rock with her head below the surface and a heavy flow of water pressing down on her."

A guide reached her 30 to 50 seconds later, he added.

Mr Stanaway said: "As he approached the board he could see Miss Jordan's right hand reaching out, however, her arm movement stopped shortly after he began his attempts to free her."

The court heard three guides tried to release Miss Jordan but were unable to do so until a rescue rope, provided by another riverboarding company, was brought to the scene about 20 minutes after she was trapped.

She was pronounced dead at the scene after attempts to revive her failed.

Mr Stanaway told the court that rescue ropes and throwbags were widely accepted within the industry as essential rescue devices in whitewater, but the company did not carry them.

He said the company should not have taken participants down the stretch of river above Roaring Meg with the river flowing at only 84 cubic metres a second. The river level had dropped, exposing rocks that were usually covered with water, the prosecutor added.

Defence lawyer Michael Parker told Judge Callaghan he would wait until the prosecution rested before outlining his case.

The trial continues.