A second vessel of interest's been identified in a drug smuggling operation that saw around 91kg of cocaine make its way to New Zealand.

A 32-year-old Australian man was arrested in Dunedin after allegedly trying to import the class-A drug.

The Victorian resident allegedly attempted to scuba dive to retrieve the drugs from a hidden compartment inside the hull of the Spirit of Auckland, a cargo ship.

While the arrest occurred in September last year, today the Australian Federal Police made an appeal for sightings of an open-cab boat in Melbourne, which it believes is connected to the operation.

The AFP says a boat was seen in the vicinity of the Spirit of Auckland in Melbourne, as it made its way to New Zealand.

It's described as having a "distinctive fish skeleton sticker on its body".

Officials are looking into whether the boat was used as reconnaissance to keep an eye out for law enforcement as the vessel passed through Australian waters.

The Australian national is due to face court in New Zealand on March 15.