The father-of-three, who was originally from Cork, drowned while rescuing his son after he slipped into water rapids in Queensland.
The tragedy unfolded at around 2pm local time on Sunday, January 2 when the family were enjoying a day out at Wappa Falls.
Mr Cowman (49), bravely managed to push his son out of the water, but he did not resurface.
The body of the Irishman, who was known to his friends as Cass, was discovered later that evening.
His wife Trish has paid tribute to her husband, whom she described as a “fabulous father” and “passionate about politics and social justice”.
“Our Irish and Australian families and friends are mourning the loss of Cassan, our father, husband, brother, friend,” she said in a statement.
“….at Wappa Falls, Cassan jumped into the falls to rescue his sons; he pushed them out of the water but was unable to save himself.
“Cassan moved from his beloved County Cork with his family to Australia 15 months ago, and was in love with our beaches, blue skies and bushland, and went exploring with his family at every opportunity.
“Cassan was a fabulous father to his three children, dryly funny and very passionate about ethics, politics, social justice, and of course Ireland beating the All Blacks in Dublin.”
Originally from Donoughmore in Cork, Mr Cowman is survived by his wife and their children Ormond (11), Ella (9), and Torin (7).
A death notice on RIP.ie states that the death has occurred of Cassan (Cass) Cowman of Queensland, Australia and formerly of Donoughmore, Cork “following a tragic accident”.
“Cassan, loving husband of Trish (Darvall) and adoring and adored Dad of Ormond, Ella and Torin, brother of Mark and son of the late Ormond and Helen,” it reads.
“Loved and remembered by all who knew him, including parents-in-law Peter and Elspeth, sisters-in-law, brothers-in-law, nieces, nephews, extended family, wonderful neighbours and community of Donoughmore and Cassan's many good friends.”
Services are taking place in Australia, with a celebration of Cassan's life to take place in Cork at a future date.
The Australian service will be available via live web stream on Wednesday, January 19 at 9.30am, AEST, (the local Irish time will be 11.30pm on Tuesday, January 18.
A GoFundMe page set up to assist his family and raise funds for his children’s education has surpassed the $40,000 AUD (Є25,000) mark.
Tracey Anne Lutton, the organiser of the page, said: “Ormond, Ella and Torin were the apple of Cass’ eye and like any parent he wanted the best for their futures.
“Cass was charismatic, Irish to a fault, but at the end of the day ultimately he simply loved his family.
“He was a devoted family man through and through, working day and night to provide for his family,” she said.
People can donate to the fund in honour of Mr Cowman at the ‘Cowman Family Education’ GoFundMe page.