An Auckland coastguard crew is in hot water after making a mercy dash to fetch bottles of tonic water for a luxury charter launch anchored up in a Waiheke Island bay.

Volunteers who made the exceptional journey across the Hauraki Gulf for a cash donation now face a reprimand by Coastguard bosses after a Waiheke resident witnessed the transfer onto a charter craft and was concerned by the on-water antics.

Those on board the high-spec boat, which was anchored off Oneroa Bay on Saturday afternoon, offered $100 cash for the Auckland Coastguard vessel to bring them a box of tonic water after they ran dry.

Coastguard New Zealand chief executive Callum Gillespie last night said he would not be accepting any money relating to the episode, admitting it was not the right use for the vessel.

The Waiheke man, who alerted Coastguard bosses about the situation, said he first noticed the rescue craft approach the bay at high speed. Thinking there was an emergency unfolding on the water he trained a pair of high-powered binoculars onto the vessel.

But as he watched from the vantage of his home some 300m away, it was apparent a different type of liquid crisis was taking place.

"I saw the Coastguard boat coming into the bay at a hell of a speed and I assumed there was some sort of emergency that they were responding to," said the man who did not want to be named.

"When the Coastguard boat pulled up behind the launch there were great cheers.

"I had my binoculars out and I didn't start taking photos until I realised what was actually going on.

"That was after I saw boxes getting transferred to the tender. It looked like boxes of wine."

The Waiheke local said once the Coastguard boat made its delivery it circled the launch and sped off.

He claimed the Coastguard vessel was being driven in a "stupid and dangerous" manner.

He had since sent two photos to Coastguard New Zealand with a request to explain the incident.

Gillespie said there was no alcohol involved, rather a single box of tonic water that was transferred to the charter after a Coastguard volunteer asked if his colleagues could help out.

"After a busy day on the water assisting boaties in need, the crew were returning to base when they agreed to respond to a fellow volunteer's request onboard a launch at Oneroa, who asked if it was possible to bring out a box of tonic in return for a financial donation to their unit.

"Despite their worthy intentions to gather funds and there being no other tasks for them we don't think that's the right use of the rescue vessel and we will be formally communicating that with the crew."

Gillespie confirmed that they circled the launch with their rescue vessel before heading home.

While there did not appear to have been any risk to anyone in that manoeuvre, that would also form part of the debrief.

He said the episode attracted a $100 cash donation which he would not be accepting.

"I don't want it," he said.

Gillespie said despite this incident Coastguard volunteers, including the crew in this vessel, did extraordinary things for communities all year round out of the goodness of their hearts.

"I would hope that this incident is understood in this context," he said.