Kate Goodchild, Luke Dorsett, Roozbeh Araghi and Cindy Low died almost instantly when their water raft hit another and overturned, crushing them.
Prosecutors laid three charges against Ardent Leisure, saying it failed in its duty of care. It did not contest them. Each violation carries a maximum A$1.5m (£0.8m; $1m) penalty.
The 2016 accident at Australia’s biggest theme park, on Queensland’s Gold Coast, sparked reforms to state criminal liability laws for companies. A coroner’s inquiry, which delivered its findings in February, had recommended prosecutors charge the company.
What happened in the accident?
On 25 October 2016, four adults and two children were on board the raft on the Thunder River Rapids ride, which simulated the experience of white-water rafting.
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Towards the end of the ride, a pump malfunctioned and caused water levels to drop. This led to the occupied raft colliding with an empty one that had drifted loose of its moorings. The raft with the passengers flipped, fatally injuring the adults. The children survived.