"Your actions in that regard was somewhat cavalier."
The judge fined Barnes $25,000 and ordered him to pay $30,000 reparation to Mr Porter's family.
Dive Spot - a company Barnes co-owns - was fined $50,000 and is to pay $50,000 in reparation.
Barnes and the Dive Spot had admitted failing to adequately warn of the dangers of the boat's propeller and failing to ensure the safety of people in the water. The charges were brought by Maritime New Zealand under Section 15 of the Health and Safety in Employment Act 1992.
Yesterday, the court heard that Mr Porter and his wife Jill moved to New Zealand from the United Kingdom in August 2008.
The tragedy had led to Mrs Porter returning to the UK.
Alysha McClintock, the lawyer representing Maritime NZ, said Mrs Porter and the couple's son Adam bore no animosity towards Barnes or his company. However, they had found Barnes' initial not guilty pleas inconceivable and the pleas had prolonged their suffering.
Ms McClintock said the tragedy could not be characterised as a "momentary lapse of judgment" as the company had no policies in respect of what a diver could or could not do.
"This is a business which is dependent on the clients getting down into the water and the dangers of propellers. He shouldn't have allowed Mr Porter to dive on the anchor."
Barnes' lawyer Peter Magee said his client and his company had significant remorse and sympathy for Mr Porter's family and acknowledged a sizeable amount of reparation was to be paid.
He said Mr Porter was an experienced diver and knew the risks of swimming under the boat.
Mr Porter had been diving with the Western Underwater Dive Club from Auckland, which had chartered Pacific Hideaway.
