A safety of a cruise ship bound for New Zealand has been brought into question after a woman died after falling in the water.

A 70-year-old woman from the United States died in Rarotonga last week after falling into the sea from a tender platform.

She was a passenger aboard the Maasdam, a vessel operated by Holland America Line.

A passenger told Newsweek the ocean was incredibly rough at the time and it was debatable if the ship should have been tendering.

The tender platform is between the main ship and a smaller ship that allows passengers to be transported to land.

Holland America Line said it was not yet clear what caused the woman to fall into the water.

"What caused her to fall into the water is unknown at this time. She then lost consciousness on the platform and could not be revived by medical staff at the scene," the company said in a statement.

An investigation was under way.

The ship is scheduled to arrive in New Zealand later this month.