Kelekolio Latu's body was found by search and rescue police in north Victoria's Narre Warren Lake after the accident on Sunday, local media reported.
Mr Latu had gone to the rescue of his 11-year-old daughter Theresa and 12-year-old nephew who were in trouble in a dinghy on the lake in Lysterfield Lake Park.
His wife, Manu Latu, told the Berwick Leader newspaper her husband would be remembered as a hero.
The pair had moved from New Zealand to Australia nearly four years ago "because he wanted to see if we could have a better life".
It was the family's first visit to the lake as a treat after church.
"It was a very happy day for him".
"He wanted to go and take the kids and his nieces and nephews."
The family had been at the lake for barely 25 minutes when the children got into trouble and he went to their rescue.
While he could swim, her husband struggled in the water and attempts by friends to pull him from the lake failed, she told the newspaper.
After an agonising wait, search and rescue police found his body several hours later.
Mrs Latu said they were struggling to come to terms with her husband.
She planned to change her 1-year-old son's name from Pita to her husband's name, "because he reminds us of him".
Friends and family have posted messages of support on Facebook.
"Your life is a blessing. Your memory is a treasure. We love you beyond words and miss you beyond measure! Rest in peace kelekolio latu you will be forever in our hearts," wrote Rina Leka Tupou.
Arrangements were being made for family and friends to travel from New Zealand for the funeral.
