An investigation into a Shotover Jet crash which left two people hospitalised has found the crash was down to driver error.
Changes to the operators' training procedures have been recommended.
The Maritime New Zealand report said the driver entered a turn at a slightly incorrect angle. It explained the boat was entering an area of disturbed water, probably allowing air under the hull, reducing the friction, therefore reducing control.
''Both of these factors affected manoeuvrability in the turn, causing the jet-boat to slide towards the left side of the river, hitting the rock wall at around 22kmh,'' Steve Rendle, from Maritime NZ, said.
Recommended changes include greater emphasis on defensive and evasive driving skills, greater mentoring and monitoring of newly qualified drivers and video footage for peer review. An officer will monitor and assist implementation.
David Kennedy, southern region manager for Shotover Jet, said existing training was extensive, but he recognised improvements could be made.
''We have been doing more driver checking and evasive manoeuvre training. Really, we are looking at everything, all areas of our training and where we can improve it.''
While the industry requirement was 50 hours' driver training, all Shotover staff had 120. He said the company had introduced more driver checking and had been working with Maritime NZ in an informal manner.
''We have to review how it will fit in with our [training] programme and we are in the middle of doing that right now.''
The incident happened on January 10 when a Shotover jet-boat hit a rock face while proceeding downstream to the second gorge on the Shotover River.
Two passengers were admitted to hospital following the accident, and four others suffered bruising and whiplash injuries.
Maritime New Zealand confirmed Shotover Jet fully co-operated with the investigation and that the driver had completed 91 hours of solo driving and 120 hours of training.