"We encounter sharks quite a bit and the big thing is to keep your cool, keep your fingers and toes tucked away, and don't do anything sporadic," he said.
More than 300 people attended Wednesday night's Fishing Media Awards, held at the Royal New Zealand Yacht Squadron in Auckland.
Mr Grundy was nominated for two awards, the Best Action Shot and the Balls of Steel award for not letting the fear of sharks get in the way of a great shot.
With 15 years' experience up his wetsuit sleeve, Mr Grundy said he'd swum with sharks up to 8m long.
"There have been a number of close calls but no attacks. When I'm diving and filming around food chain areas, you have to get really close to get the action shot and the sharks definitely want to see who you are," he said.
When asked what he was thinking when the mako shark approached him, Mr Grundy said he was primarily concerned about making sure the camera was rolling and in focus.
"You just have to keep facing them, show you're not scared and even swim towards them a bit. Nine times out of 10, they'll keep their distance," he said.
Mr Grundy said it might be the electrode impulses or the reflective lens of the camera that lured the sharks towards him when filming.
Originally a roofer, Mr Grundy began his underwater adventures as a hobby and has since worked for the ITM Fishing Show for six years.
Despite her husband's hazardous occupation, Grundy Productions producer Nicky Grundy said she didn't worry too much.
"I'm so used to it. I should probably get an award for not stressing," she said.
While his occupation might seem crazy to most, Mr Grundy said he didn't consider himself an adrenaline junkie.
"It's what we do, we enjoy doing it and we'll do it again tomorrow," he said.