Elated marine biologist Dr Ingrid Visser says it hasn't quite sunken in yet that the orca is now finally free.

"We managed to cut the line and we followed him for a while after that and he seemed to be doing okay," she told Newshub on Friday.

Dr Visser had spent the past four days attempting to free the orca from the cray pot line it became tangled in near Tutukaka in Northland on Sunday night.

The team thought they'd lost track of it, but shortly after midday on Thursday, a whale-watching vessel from Auckland Whale & Dolphin Safari spotted it near Auckland's North Head and tipped off police.

Newshub followed the orca around on Thursday from Westhaven to Island Bay. In that time, it rarely moved at a speed above 4 knots, while the average orca swimming speed is 8 knots - which showed just how badly the injury was impeding it.