While New Zealand has the no-fault ACC scheme, meaning legal action cannot be pursued here, the passengers who are part of the legal action signed the cruise contract while in Australia.
Lawyer Rita Yousef, from Sydney-based Stacks Goudkamp, told AFP News that at least one Australian family and a "number of others" would sue for alleged negligence, breach of contract and violations of Australian consumer law.
She said that there had been "no indication at all that Royal Caribbean was paying attention to" the increased risk of the volcano erupting.
"At the very least they should've informed their tour participants of the risk and let them decide if they wanted to take the risk," Yousef told AFP.
"We can go one step further and ask why were they even running these tours when there was such high risk? Why were they not cancelled?"
Survivors of the eruption were left with "absolutely profound and unimaginable disability, the kinds of burns that a lot of medical professionals have never seen in their lives", she said.
Relatives had to watch their loved ones suffer in pain and were coming to terms with the kind of quality of life they were left with.
The cost of the ongoing medical care and rehabilitation the injured needed would likely exceed the New Zealand compensation they were entitled to, she said.
Yousef said she hoped that the legal action would hold the cruise company to account for its failings.
In a statement, a spokesperson for Royal Caribbean said since the eruption the company has "focused on providing care and support to passengers, their families and crew that were impacted by this event".
"The details of the tour are the subject of two separate investigations in New Zealand which we will be fully co-operating with and we are unable to provide further details at this time."
In New Zealand, WorkSafe and the Coroner were investigating the disaster.
