If the pool pump was involved, it would not be the first tragedy of its kind.
In 2009, British schoolboy Nathan Clark drowned at a Thai water park after apparently being sucked into a pool's pumping system.
And a 12-year-old Russian girl died after she was reportedly trapped underwater when her arm was sucked into a swimming pool pump at a Turkish resort last summer.
Father-of-three Josias Fletchman, who attempted to save the lives of the three holidaymakers, said she "stayed calm" as she touched her loved ones' and prayed their hearts would start beating again while he tried to save her husband's life.
The 35-year-old from Manchester told yesterday (WED) how he returned to the apartment block where the triple tragedy occurred as staff at holiday complex Club La Costa World were pulling the three out of the water.
Mr Fletchman described the family as being of Afro-Caribbean descent like him and from the London area.
Mr Fletchman said: "The mum was praying for them to come back to life.
"She was calm. She was touching their bodies. She continued praying even after the ambulance people arrived and had stopped trying to revive them.
"She exercised her faith to the limit. I was performing CPR on her husband but I'm a believer and I prayed as well.
"She strengthened me in the way she reacted. It just wasn't meant to be."
Eni Raja, 22, originally from Norway but now living in Birmingham, added: "I saw the bodies with the three white blankets over them.
"The mum was crying. I can't get the image out of my mind."
Local reports say police have also searched for any items of clothing that might have got stuck in the pool drain and taken water samples to test ahead of the autopsies, which were due to take place on Christmas Day at Malaga's Institute of Forensic Medicine.
The results of the autopsies will be passed on to an investigating judge but are rarely officially made public in Spain.
The names of the father and two children have not been released. Well-placed sources have confirmed the nine-year-old and her father were British, but the 16-year-old was travelling on an American passport.
Trained counsellors are now spending time with the mother and her other child, thought to be a teenage daughter, while other relatives fly to Spain from the UK.
Costa Club World spokesman Juan Jose Millan said: "The pool has all its paperwork in order and what we know from the Civil Guard is that there is no anomaly with the pool suction system which press reports have highlighted.
"But for us the most important thing at the moment is to care for the family and enable them to get the privacy and rest they need right now.."
He added: "This has been a terrible occurrence and staff and some guests are receiving psychological support along with the family."
Although Mr Millan said the pool where the triple tragedy occurred had been closed "as a precaution" there was no police tape around it yesterday (WED).
Some guests of the hotel had placed candles as a memorial to the three who lost their lives.
A Foreign and Commonwealth Office spokesman said after news of the tragedy emerged: "We are offering assistance to a British woman following an incident in Spain."
