A two-year dispute between Queenstown jet boating companies Thunder Jet and Kawarau Jet continues in the Environment Court on Monday.
Kawarau Jet is trying to stop Thunder Jet from operating on the same stretch of the Shotover River.
Thunder Jet began operating on the Shotover two years ago, but was forced to pull its boats from the water after Kawarau Jet challenged its consent.
A hearing in 2009 allowed the company to go back on the water, but that was appealed by Kawarau Jet, which cited safety concerns.
Thunder Jet is partly owned by Neville Kelly and his brother Sean has a stake in Kawarau Jet.
Thunder Jet has always said it operates safely, but Kawarau Jet maintains two different companies cannot operate on the same stretch of river.
The court hearing is expected to take 10 days.