The Great Barrier Reef Marine Park Authority is investigating Senator Pauline Hanson's trip to the reef after she was photographed handling a piece of coral.

Senator Hanson and two of her colleagues travelled to Great Keppel Island last Friday to hit out at "untruths" told by green groups about the reef's health.

She was photographed holding up a piece of coral while snorkelling, which was not allowed under a zoning plan unless a research permit had been granted, a spokesman for the Great Barrier Reef Marine Park Authority said.

"We understand one of the parties involved has an existing research permit, which outlines conditions for coral collecting, including species, size, location and equipment," the spokesperson said in a statement.

"We are seeking further information on the activities - and reviewing the conditions of the permit - to determine what follow up action, if any, is required."

Senator Hanson also faced criticism for holding her media event far from where the worst of the coral bleaching has occurred.

Conservationists said Senator Hanson should have instead travelled to Lizard Island, more than 1000km away, where the worst of the bleaching is located.