The boat's skipper has denied charges laid against him and will appear in court later this month.
On February 23, 2014, he decided though conditions were "marginal" it was safe to set out on the trip as long as they returned before midday when rough seas were forecast.
The party of 40 was made up of 36 customers - including children and a pregnant woman - McPherson, the skipper and two staff.
Dolphins were spotted as they sailed beyond the Rangitoto channel but travelling north, weather conditions deteriorated.
Without warning, the boat's skipper turned away from the impending squalls, knocking two passengers on the foredeck over.
Large waves crashed on to the deck and water was reportedly knee-deep within a short period of time.
"Passengers described the boat going up and coming down, heard loud crashes and bangs and 15 minutes of vicious juddering," Judge Claire Ryan said.
With the bilge alarm sounding, the captain instructed a staff member to activate the pump but the court heard today he did not know where it was situated or how to use it due to inadequate training.
There were also issues with lifejackets.
Though staff had demonstrated how to use them at the outset, when people started to retrieve them there were different styles with which they had not been familiarised.
Coastguard staff eventually managed to scoop up all on board and pumped out the vessel to keep it afloat.
Judge Ryan was shocked to hear the only person on board who was maritime-trained was the captain.
"No one considered what would happen if he had been incapacitated or injured... no one else could've handled the boat," she said. "It's extraordinary, I must say."
Dreamweaver Charters Limited had owned and operated the boat between 2003 and 2011 until McPherson took over the day-to-day running but by law, the company must ensure it is operated safely.
The company's lawyer Henry Steele said his client mistakenly thought responsibility rested solely with operators and while the judge accepted that, she did want to see them simply pass the buck.
"We have an incident that could've killed somebody and that's the bottom line," she said.
Judge Ryan said McPherson had sacked the captain since the incident and taken substantial measures to improve operational safety.
She was also quick to point out the substantial damage to the catamaran on the day in question was completely unforeseeable as regular inspections had taken place.
