Sebastian Eubank, the son of boxing star Chris Eubank, died from a massive heart attack while in the sea watching the sunset in Dubai, his widow has said.
Following a post-mortem examination, Salma Abdelati said her husband had a "pre-existing heart condition" which was not previously known about.
Eubank died last Wednesday just days before his 30th birthday and a month after he became a father.
His widow said Eubank probably could not have been saved even if he had been out of the water.
She has spoken of her pain but said it was "of some comfort" that he lost his life after "having one of his favourite meals", and he had been at his "favourite place" in the United Arab Emirates city when he died.
She also said she was "grateful" that Eubank had spent several "happy weeks" with his young son Raheem.
Salma Abdelati said in a statement: "Dubai police and the coroner have confirmed that after a full post-mortem Sebastian Eubank tragically died from a massive heart attack whilst in the sea and probably could not have been saved even if out of the water.
"There was evidence of a pre-existing heart condition we were all unaware of.
"While still very painful, it is of some comfort that Sebastian died after having one of his favourite meals with one of his closest friends whilst doing his favourite thing at his favourite place in Dubai where he often went to swim.
"He was standing in the water close to shore watching the sunset at Cove Beach in Dubai.
"I am grateful that he was able to spend a few short and happy weeks with his son before his death.
"I would like to express my profound gratitude to the Dubai coroner for conducting a swift and thorough investigation and to Dubai police and in particular the victim support department for their help and support at this difficult time."
Sebastian Eubank – a boxer and personal trainer and the third oldest of Eubank’s children – had been living in Dubai.
Chris Eubank said he was "devastated" by his son’s death and paid tribute, saying he was a "deep thinker who liked to challenge and accepted wisdom".
He had followed his father and brother Chris Eubank Jr into the ring, starting a professional boxing career with two victories.
Eubank Snr said in a statement: "Never did I ever imagine I would write these words or experience the feeling I now have at the loss of my son. My family and I are devastated to hear of the death of Sebastian just days before what would have been his 30th birthday.
"He leaves his wife Salma, his son Raheem born just a month ago, his mother Karron Meadows, brothers Nathanael, Chris Jr, Joseph, one sister Emily and countless relatives and friends."
World champion boxer Chris Eubank Jr also paid tribute in a series of posts to his brother.
The WBA interim middleweight champion said that before Friday, he had not cried since he was 12, but on Friday he "cried the whole day".
He said in a series of tweets: "My brother Sebastian Eubank was a special man… a righteous man… who always put others before himself.
"A man of many talents, boxing, MMA, poetry, music, coaching, cooking the list goes on but the most important thing to him was helping others less fortunate than himself.
"I haven’t cried since I was 12 years old… yesterday I cried the whole day. I’m sorry I wasn’t there to watch your back like a big brother’s supposed to. Can’t believe you’re really gone man but you’ll always be in my heart, mind & spirit."
Chris Eubank Jr promised to continue to care for Sebastian’s young son.
He added: "Now your legacy will live on through your beautiful new born son & I will treat him like my own. Watch over us until we meet again young lion."