The company pleaded not guilty to the charge and a trial began shortly after 10am before Judge Noel Sainsbury.
The prosecution says Kava effectively died as a result of "inadequate" safety measures.
However the defence deny that.
The trial is expected to run for four days.
The first witness called was Samson Somers, the son of company director Andrew Somers.
He said the charter business was family run and he had much experience as a result.
He earned his skipper's ticket at 18 and had previously been granted an exemption from Maritime NZ at 17 to skipper before that.
Somers said he had spent a significant amount of time on the boat Kava fell from.
He explained to the court about the area where Kava fell.
The area was known as the duckboard and housed the boarding ramp and a BBQ for passengers.
The area was blocked off by a plank most of the time but when the BBQ was in use passengers who were authorised to cook - a maximum of two people - were allowed there.
When the BBQ was in use the plank was removed and replaced with a metal chain.
Somers said a safety briefing was carried out with the BBQ-approved passengers.
That briefing included instructions to the passengers that only they approved people
could be in the area and no others.
He also gave a safety briefing to the passengers over the PA system before they set off.
He could not remember whether he explained at that time the specific rules for the BBQ and duckboard area.
Somers spent some time explaining to the court how the boarding ramp was secured with a lock mechanism.
He said he secured the boarding ramp himself the night Kava died.
He was certain the ramp was secured properly and there is no way the "snug-fitting lock" could have "rattled out of position" easily.
"It had to be pulled and wriggled to be pulled out of the ramp," he explained.
Prosecutor Sam Lowery pressed Somers on how sure he was that he had secured the ramp
and that the lock was not damaged.
"100 per cent sure," the skipper replied.
He went on to say there was "no damage" to the ramp itself.
Somers was asked about the number of passengers on the duckboard.
He conceded that at one stage he spotted "roughly five or six" people near the BBQ and he sent crew members down to remove them.
The passengers were ushered off the duckboard and the safety chain was put back in place.
After Kava went into the water Somers went to the duckboard.
The ramp was in the water and Somers pulled it back into a vertical position.
He said there was damage to the ramp - it had buckled.
A rope used to hold it in place was also damaged.
He told police on the night that he had been able to push the lock back into place - but in court today said he could not remember if that was the case.
After he pulled the ramp back on board he heard a splash and saw another man in the water.
Somers said it looked like the man had jumped from the top of the boat.
The boat was idling at the time as people were looking for Kava and man overboard procedures were underway.
When questioned by the defence Somer said he was "very comfortable" around boats, having grown up being on them.
He has also worked on cruise ships.
Somers said he was experienced, competent and had multiple qualifications relating to boating and security awareness and crowd control including basic first aid and fire fighting.
He said The Red Boats was "very safety concious" as a company and he had been doing safety drills with his father and grandfather since he was a child.
The company was "very responsive" to any maintenance that needed done on its vessels.
Somers said his training was "continuous" and he was "always learning" and upskilling.
He said safety checks were done by the crew throughout the charter - every 10-15 minuttes - including making sure no one was sitting or leaning on rails or standing on seats.
The court also heard from crew member Bradley McKinley who was working in the bar the night Kava died.
He reiterated to the court that the duckboard area, from which Kava fell to his death, was not for passengers while the vessel was moving.
"It's purely for loading and unloading," he said.
"It's not necessarily enclosed."
McKinley told the court that "the individual selected to use the BBQ" was permitted to be on the duckboard.
"That was set out by the owners when I started working there - it was a non-passenger area and it always has been," he stated.
He confirmed that there were two measures in place to prevent unauthorised passengers going to the duckboard - the plank and the chain.
McKinley also spoke about the boarding ramp that Kava reportedly leaned on and fell from.
He said unless it was manually unbolted, "it should not come undone".
At one stage when there were more than the authorised passengers on the duckboard, McKinley went and asked the extra people to move back to the main area of the boat.
He explained to them that the duckboard was not strong enough to hold all of their weight and they were not permitted to be there.
McKinley was at the bar when Kava went into the water.
"An individual came up to me and calmly said someone had gone overboard," he said.
Somers overheard this and the emergency procedures were put into place.
When McKinley got to the duckboard there were a number of people out there and the boarding ramp was "dragging" in the water.
The trial continues and Judge Sainsbury is expected to hear from five further prosecution witnesses including crew and passengers who were on the boat the night Kava died.
