Mr Hannah said it was the first time in 12 years of kayaking the harbour and coast that he had seen dolphins, so he gave up on the idea of fishing.
"It was very exciting to see them up close. I was amazed at the size of them."
He had a few moments of pause when a dolphin breached beside him but they seemed more interested in feeding, he said.
"It was pretty lucky," he said.
"It certainly made it hard to come back to work."
The University of Otago, Portobello marine centre and the Department of Conservation all received calls from people who had seen the dolphins.
Doc marine ranger Jim Fyfe said it was not uncommon for groups of bottlenose dolphins to visit Otago Harbour in summer.
In past years they had been regular visitors and one year a pod stayed a week and even calved in the harbour.
Not much was known about where the dolphins were transiting to or from, he said.
Jet skiers and boaties were reminded to travel no faster than idle or "no wake" speed within 300m of any marine mammal.