Two French tourists were pulled from the ocean within five minutes of each other after having fatal heart attacks while snorkelling on Australia's Great Barrier Reef on Wednesday morning.
On Thursday, Sydney cardiologist Ross Walker told news.com.au he believed Danielle Franck, 74, and Jacques Goron, 76, suffered stings from the tiny, highly venomous Irukandji jellyfish.
"Look at the facts here. You have jellyfish infested water, and the bite of the jellyfish stimulates a heart attack," Walker said.
“I think they were more likely all bitten by Irukandji jellyfish.”
But managing director of the company responsible for the snorkelling trip, Passions of Paradise, Alan Wallish, said he couldn't see how "jellyfish or stingers would have contributed in any way" to the fatalities.
"We don’t get Irukandjis at this time of year and the two parties were very separate," he said.
“The lady was 15 metres away from the boat ... [and] had a full stinger suit on."
Irukandji are the smallest and most venomous box jellyfish in the world.