Pettigrew admitted he still struggled every time he shared such footage and had recently slowed down in doing so.
"I really worry that if I put it out, 'is this doing any good?'. Every time I go to do it, I think 'don't do it' just because people look at what I do and they want to do it."
Pettigrew is the only non-commercial and non-research person that he knows of to hold such a marine mammal permit in New Zealand. Getting close to some marine life without one is an offence and, in cases involving leopard seals or whales, dangerous.
But Pettigrew has been heartened to know his messages of "how we interact with marine mammals and what we can do to look after them" are being heard.
"A lot more people know that there are rules now. I was with a pod of orca in 2015 and there were people everywhere and DoC didn't get any complaints. A year later I was with a pod of dolphins again, same scenario, and DoC got seven complaints. That shows it's working, but there's still a lot of people that really need to slow down around them."
Pettigrew said Tauranga Harbour was teeming with marine life, which could be easily be spotted if you knew where to look. He would offer his tips to help people see what they could, without breaking any rules.
What you need to know
What: Nathan Pettigrew, Stories, Experiences and Conservation
Where: Toi Ohomai, Windermere campus
When: Thursday, 7pm to 9pm
Cost: The event is free but registration is essential. Register via Toi Ohomai's Facebook page.