Harbourmaster reviewing America's Cup boat's close encounter with Auckland ferry

Defiant got very close to an Auckland ferry.

The Auckland Harbourmaster is examining a close call between American Magic's AC75 America's Cup boat Defiant and a ferry.

Footage emerged of Defiant sailing very close behind a ferry traveling to Waiheke Island from Auckland on the Waitematā Harbour before being forced to make a sharp right turn.

When contacted by the Herald, an Auckland Transport spokesperson said Harbourmaster Andrew Hayton was "looking into it" and forwarded the following relevant rules.

The collision prevention rules, which were clarified as applying to all vessels, states that "any alteration of course or speed or both to avoid collision must, if the circumstances of the case allow, be large enough to be readily apparent to another vessel observing visually or by radar. A succession of small alterations of course or speed or both should be avoided".

It also states that "action taken to avoid collision with another vessel must be such as to result in passing at a safe distance'.

In the footage, the ferry's captain can be heard saying, "I've got to slow down … I don't know where that yacht's gone."

Aleysha Knowles was aboard the ferry, and watched the nerve-racking moment unfold.

"My boyfriend is a captain on a super yacht, so he was telling me that surely the ferry would slow down because of the maritime rule 'power gives way to sail', but he just didn't," she said.

Another yacht can be seen in the background of the video, which is thought to be a Team New Zealand boat.

The United States syndicate's Defiant tipped over earlier this month while training on the eastern side of Browns Island, reports Sail-World.

The boat quickly recovered with no apparent damage to continue sailing.

The incident showcased the safety features of the AC75, suggesting the boats will be able to be pushed to its limit and recover from any mishaps, unlike the AC50 and AC73 boats in the 34th and 35th America's Cups respectively.

Team New Zealand also capsized their AC75 Te Aihe back in December but were also able to quickly resume training.