A video of the police anti-terrorist team sliding down ropes on to a Cook Strait ferry in a helicopter training exercise shows why passengers saw the incident as a near-disaster.
The clip shows five members of the elite Special Tactics Group sliding down from a Helipro helicopter, which then lifts back towards the trailing Westpac rescue helicopter.
The rescue helicopter banks to the left before pulling back from the approaching aircraft, piloted by Helipro's Rick Lucas.
Passengers watching can be heard talking about the move, with one calling it "really dodgy". Another says: "He didn't think he was going to come back on him, eh? He had a bit of a surprise coming back at him."
The note posted on YouTube with the video praises the rescue helicopter for "quick thinking" to avoid a crash, saying without it "a mid-air collision would have occurred". At least eight people were on the two aircraft.
Mr Lucas said the move was carefully planned and what was seen as a near-collision was actually a move carried out exactly as intended.
He said video footage of the training exercise was three years old, although was posted online just days ago, and gave a "distorted impression".
"We briefed the whole exercise prior to the event. The briefings are extensive. All pilots and all crews were aware of each other."
Westpac rescue helicopter operations manager Dave Greenberg said the staff had since left. "Everyone took the action they needed to ensure there wasn't a collision."
A police headquarters spokesman said it was understood there was no risk of a crash but "operational repositioning" was required.
He said both aircrews were fully briefed by the lead pilot and were able to see each other at all times.