But when he saw "two floating heads" at least 200m offshore, the volunteer lifeguard knew they were in trouble.
"No one goes swimming out there, there's no waves or anything," said Dickson.
"People don't go out there on purpose. It's always people that are out there stuck."
So the 21-year swam to them, his boogie board attached to his wrist.
"They were a long way out, so it took me a while to get there."
And then they disappeared from his sight.
"That got me going a wee bit," he said.
"I thought, 'here were go, it's gone bad quite quickly'."
Dickson floated for a few minutes, looking for them and was "very relieved" when he spotted the two, who had drifted further south than he expected.
"It's pretty unforgiving out there," the off duty volunteer Surf Lifeguard said.
"It took me a few minutes to get out there. That's all it can take sometimes."
Dickson said the swimmers, a woman in her 30s and a 12-year-old boy, were floating on their backs.
"They were nice and relaxed, floating on their back, doing exactly what they should be doing in that sort of situation," he said.
He let the exhausted pair rest on his boogie board for a moment to catch their breath.
They had both swallowed water and the boy couldn't swim, Dickson said.
"The woman must've been a really good swimmer to keep them up for that long."
"Apart from being exhausted, they were quite relaxed. That was definitely the reason they'd stayed afloat for so long."
Using the boogie board as a flip board, the woman and Dickson kicked back to shore, an arm around the young boy.
The exhausted woman lay down on the sand, where she and the 12-year-old were treated by emergency services.
Dickson was later told the pair had been in trouble for at least 10 minutes before he reached them.
Others had tried to grab the swimmers as they were swept out, but weren't strong enough in the water, he said.
Dickson's quick reaction was due to instinct and experience, honed by six seasons of Surf lifesaving, he said.
With no lifeguards patrolling, he knew an ambulance would be at least 20 minutes away, and that a Surf Life Saving team would take longer.
"I can't describe how lucky I think it all was," he said.
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It was the second rescue by an off-duty volunteer Surf lifeguard that day, following another rescue only hours earlier at Otaki Beach, less than an hour's drive away.
Peter Housiaux was out walking his dog at around 4pm when he saw three boys dragged into a rip.
One of the trio was able to swim back to shore, so Housiaux, after putting the boys on a boogie board they had, helped them return ashore.
Surf Life Saving New Zealand has urged beach-goers to heed their safety advice over summer, saying that the alternative could lead to tragedy.
"The rescues mean there are four people who will be home with their families for Christmas," Chief Executive Paul Dalton said.
There have already been 25 drownings between the beginning of January and the end of October this year, topping last year's total of 23 in the whole year.
Surf Life Saving New Zealand's Charlie Cordwell said the rescues served as a reminder of the safety measures the club advises, the "3Rs".
"If you get caught in a rip, remember to Relax and float, Raise your hand to signal help and Ride the rip until it stops, so you can swim safely back to shore."
People should also choose a life guarded beach and swim between the flags, he said.
Those swimming at a beach that isn't patrolled should be incredibly careful and never swim or surf alone, he said.