A blockade at the entrance to the Hole in the Rock could be the next step in a long-running dispute between tourism operators and the island's Maori owners.
The trust which owns Motu Kokako Island started a direct action campaign this month after negotiations failed with the three companies taking tourists through the Hole in the Rock.
The Motu Kokako Ahuwhenua Trust believes tourism operators profiting from the island should pay a fee in the same way companies pay a concession to run ventures on private or conservation land. It is also concerned tourists are not being told the correct history of the culturally significant island.
This week trust members have been handing out leaflets on Paihia wharf and trying to discourage potential customers from taking the cruise.
They have vowed to ramp up their protests in coming days before possibly taking their action to the water.
Chairman Rau Hoskins said the trust would consider a blockade of the hole's entrance if the three tour companies - Fullers, Explore NZ and Mack Attack - did not enter into new negotiations.
"It will be about us making it very clear to both the operator and the tourist that there is a significant issue here and we feel that our mana is being trampled on by these operators," Mr Hoskins said.
Trust members had been handing out leaflets to visitors who had been on the cruise or were considering going on it.
"Several people who hadn't yet been on a trip said they would now reconsider doing it after reading our information," Mr Hoskins said.
"We've got some other plans which will be more directly aimed at the operators."
The row first erupted in 1987 when Fullers raised a flag on the Maori freehold island Motu Kokako, also known as Piercy Island.
The following year, the tour operator agreed to pay a portion of each fare to the trust.
When another operator started a similar cruise, the trust and Fullers took the firm to court alleging trespass.
The High Court threw out the case in 1992, ruling that access to the open sea could not be impeded under maritime law.
Fullers, which believed the payments gave it exclusive rights, then stopped paying.
The three operators and the trust have been negotiating for the past five years but talks broke down when the only offer the trust received was deemed "insulting".
Mr Hoskins said Mack Attack bosses visited the protest on Tuesday to advise they were drawing up proposals.
Explore NZ earlier told the Advocate paying the island's owners to pass through the Hole in the Rock when there was no legal requirement to do so could set a risky precedent.
Fullers GreatSights said it had entered into many discussions with the trust over the past five years, culminating in an offer to work with the trust to ensure its mana was properly recognised.
The company had not received a response to that offer.