Carnival Spirit was forced to deal with swells of up to nine metres outside Sydney Heads, after the NSW Port Authority closed the Sydney Harbour port on Tuesday morning, deeming the conditions to be "far too dangerous".

A spokesperson for the NSW Port Authority said there were seven ships in Port Botany and eight others within a short distance that were also affected by the closure, meanwhile at the Port of Newcastle, the world's largest coal port, there were approximately 21 ships affected.

The Carnival Spirit was returning from Fiji and was scheduled to depart with another load of passengers.

It is likely passengers will be stuck offshore until Thursday, or until a harbour pilot can safely board the Carnival Spirit and direct the vessel into the port.

Melbourne resident Diane Armstrong, who is stuck on the Carnival Spirit, told Fairfax Media that although morale was relatively good there were a number of disgruntled people who have missed work and are worried about their pets.

"It was very scary, there were huge seas," Ms Armstrong said. "Somebody said they came down the stairs and there were people in the stairwell huddled together, scared out of their wits.

"Somebody's got their dog at home. It was arranged to be fed up until yesterday but he hasn't got anyone's phone number to tell them the dog still has to be fed."

Ms Armstrong credited cruise staff on board, but said it was hard to shake the overall feeling of trepidation.

"My sister has Parkinson's and has extreme anxiety, so I took her to the doctors and they gave her something to take," she said.

"We're a little bit concerned about where we are going and what's happening. We're on a floating island and we should have been home."

Chief Operation Officer at the Port Authority Phil Holliday said

suggestions to let passengers off at either Queensland or Victoria would be a "logistical nightmare".

"Hopefully either [Wednesday] or the day after we will be looking to get the ship in," Holliday said. "We're in agreement to ride the storm out here and we will get them in as soon as possible."

Holliday said the vessel was not burning any fuel at sea, which meant theoretically it could stay there for weeks if the storm was to continue ravaging the state like it has done in previous days.

"She [the ship] is effectively just using the bare minimum to maintain her course and speed," he said. "There's no immediate danger."

A Carnival Spirit spokesperson said they were been in regular contact with the Port Authority and was adamant the ship has ample food and fuel supplies.

With Lisa Visentin