One of 12 Australians on board a small cruise ship robbed by pirates on the Amazon River says she is only now coming to terms with what happened.

Melbourne woman Christina Ibbotson, 60, was on board MV Aqua when the boat was ransacked by pirates in Peru last week.

Speaking from Peru, Ms Ibbotson says for nearly half an hour she did not know if the other passengers had been killed or if they had been taken hostage.

"It was just a terrifying, terrifying experience," she said.

Ms Ibbotson says the worst thing was not being told that there had been a similar attack on the same boat in the same place the week before.

She says the boat's owner and the police have been slow to react and that tourism will suffer.

"I don't know what measures they can put in place going forward," she said.

"Having the boat shadowed by the military and guns and all sorts of things on board ... would make people confident."

Ms Ibbotson says she is angry that passengers were not warned of the danger.

"We know that it's causing consternation in Peru just by talking to people because they rely on tourism," she said.

"The communique that we got just two hours ago from Aqua says they [are] very disappointed, they're very sorry."

The Department of Foreign Affairs says travellers should exercise a high degree of caution in Peru.