When Carl McDuff left for work on Monday morning in Ngatea he didn't expect to be greeted by a pod of dolphins swimming in the Piako River.
The surprise was so great, he told Newshub, he did a double-take.
When he rang his wife Lorraine to tell her she didn't believe him either, asking for photo evidence to prove it.
"I said 'I've just seen dolphins'," McDuff told Newshub."And she goes 'no, you're telling a fib'."
Born and bred in the area, McDuff, 50, says he has never seen such a sight in all his years living near the lowland river system that drains into the Firth of Thames on the North Island.
Now with the video footage to prove it, McDuff says it was "quite surreal" to see the dolphins swimming in the muddy water of the river.
"I had to do a double-take to see I wasn't imagining things," he said. "[It's the] first time I've ever seen dolphins up that far."
"I was thinking when I saw them, I hope they don't get bloody stuck up there."
The footage was taken near Kaihere Rd, in Ngatea.
McDuff says after initially filming the pod swimming up the river, he and few mates also caught them swimming back towards the sea, filming from a rowing pontoon near Hauraki Plains school.
He estimates there were around 60 of them, though it was hard to be sure as they were "streaming past over a five, 10-minute period".
Hannah Hendriks, from the Department of Conservation's marine mammals' team, told Newshub that though it's not a common occurrence, dolphins do find their way up rivers on occasion.
"The reasons for this are probably that they are following food or escaping predators," Hendriks said.
She said it looked like the dolphins seen by McDuff were bottlenose dolphins.
While every now and then dolphins do get caught upriver by a falling tide, in most cases they find their way out without problem, Hendriks said.