The tragedy happened while the 22-year-old was on a tour around a small island near Phuket on Tuesday.
Thai police claim he had been drinking and had jumped into the water multiple times before he got into trouble.
Paramedics performed CPR but were unable to save him.
A Department of Foreign Affairs and Trade (DFAT) spokesperson is providing consular assistance to the family.
“We send our deepest condolences to the family at this difficult time,” a DFAT spokesperson said.
“Owing to our privacy obligations we are unable to provide further comment.”
The man has not been publicly identified.
