The tourist boat involved in the accident at Horizontal Falls in Western Australia last week "did not capsize", according to the Australian Maritime Safety Authority (AMSA).
The finding came after the government authority inspected the vessel involved and the scene of the accident, as a part of an ongoing multi-agency investigation.
"At this stage of the investigation, AMSA can confirm that the vessel did not capsize, no people fell in the water and appears to have collided with a rock wall," a spokesperon said.
As a part of the investigation, the authority also interviewed the tourism operator's company personnel on-site.
Twenty-six tourists and two crew members were on board the vessel during the incident at 7am on Friday.
Several people were left with serious injuries which required surgery, medics say.
Police claimed at a press conference on Friday that "a number of people did find themselves in the water".
Officers also commended the efforts of tour operators to get patients back to pontoons.
However, in a statement, the operator Horizontal Falls Seaplane Adventures said the boat did not capsize and immediately returned to the pontoon.
AMSA said it has issued a prohibition notice to the domestic commercial vessel and a direction notice to prevent the operator using any other vessel to transit the Horizontal Falls pending the outcome of the investigation.
"AMSA has also issued an emergency suspension of the master's Certificate of Competency," a spokesperson said.
The spokesperson said "as the investigation is ongoing no more details will be disclosed at this time".
"The findings of the investigation will be released in due course," they said.