Sunderland forward Duncan Watmore was on the fishing boat in Barbados when it was hit, and broken in two, by a catamaran.
He managed to haul three elderly passengers out of the water from the boat just before it sank.
His father, Ian Watmore, said the catamaran had "just ploughed straight into the boat and ripped it in half".
"They saw it and just assumed it was going to go round them and, when they realised it was coming straight at them, they started yelling and screaming but nothing changed," he said.
"These catamarans are quite powerful and the blade just ripped the thing in half."
Watmore had been in Barbados in February, recovering from an operation on a cruciate knee ligament injury, when the crash happened.
One of the guests on the boat had just had a hip replacement, one could not swim and the other was over 80, his father said.
After the crash, his son "clambered up on to the catamaran" and lifted them, and the skipper, out of the water just as their fishing boat sank, he said.
The 23-year-old footballer used his T-shirt as a tourniquet for the woman's leg, which was "bleeding heavily".
It was only afterwards that "shock started to set in", Mr Watmore Snr said.
"All the guests were coming up to him and telling him what a hero he was and I think the whole thing was just very disorientating for him," he said.
The rescue had been a good test of the strength of his knee, though "not one you'd plan", he added.
It is not known how the catamaran came to hit the fishing boat but it is believed its skipper was taken away by police.

Gary Watson was the frontman of The Lapelles who recently performed at T in the Park and the Belladrum festival.
A post on the band's Facebook page said Mr Watson died "as a result of injuries sustained in a tragic accident" on Saturday night.
Police said the death was not suspicious.
Emergency services were called to the River Clyde near Glasgow Bridge at about 22:00 on Saturday.
Mr Watson was rescued from the water and taken to Glasgow Royal Infirmary but later died.
The Lapelles statement read: "It's with shock, heavy hearts and sadness that we have to let you know the news that Gary sadly passed away this morning as a result of injuries sustained in a tragic accident last night.
"Today was his 22nd birthday. We are lost for words and struggling to process such a tragedy.
"Gary was a creative force, a man who without his vision this band wouldn't exist. We have lost a friend, a brother, a hero. At the moment it doesn't seem real.
"We send our deepest condolences to Gary's family and would appreciate your respect in allowing them & us some peace whilst we grieve. Forever in our hearts, with peace you go. X."
The band were due to head off on a UK tour in October.
Tributes were paid to Mr Watson on social media by fans and fellow bands.
Franz Ferdinand posted on Twitter: "We're so sad to hear of the tragic passing of @TheLapelles Gary Watson, a lovely, talented man. Thoughts are with his family, friends & band."
A Premier League footballer saved three holidaymakers after a boat crash, it has emerged.
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Tributes have been paid to a musician who died after falling into the River Clyde in Glasgow the day before his 22nd birthday.