Orca have been spotted from the tourist boat five times in the past four months, while records of sightings from the boat, going back 17 years, show only four other sightings.
The Orca have been spotted in the harbour entrance and swimming slowly, close to the shore.
"One group came right underneath the boat. You could have just about reached down and touched them."
But while the Orca sightings have excited Mr Heseltine, at the same time dolphin sightings are down, with fewer than half the usual number of dolphin sightings recorded this summer.
The most common dolphins seen were Dusky and Hector's dolphins, Mr Heseltine said.
Department of Conservation marine ranger Jim Fyfe said it was possible the presence of Orca was causing dolphins to give the area a wide berth, although that was pure speculation.
It was likely to be the same pod of Orca spending time in the area. Orca had been seen from the boat as recently as last month.
It was not unusual to see Orca off the Otago coastline, particularly at this time of year, although the sightings were interesting, he said.
He would need to go back through the Doc database of Orca sightings to see if the increased sightings were just in the harbour entrance area or if sightings were up throughout the region.
"There is certainly food available for Orca in the vicinity and maybe they are cottoning on to that fact."
