Gardaí in Cork believe that the three Noonan family members whose bodies were found in a tributary of the River Blackwater on Monday may have drowned some 24 hours before they were discovered.
It is thought Emma Noonan went swimming some time on Sunday and got into difficulty, and that her mother and brother jumped in to rescue her.
Gardaí in Fermoy are asking members of the public who may have spotted the Noonans near Awbeg River on Sunday to contact them.
Funeral arrangements have yet to be finalised.
Emma Noonan, a 20-year-old hotel worker, was hoping to train as an apprentice accountant. She had organised an interview with a firm which was due to take place later this month.
The former student at Cork Institute of Technology had gone for a swim in Awbeg River, but found herself out of her depth. Her brother David (24) and mother Ita (49) jumped in to help her but all three drowned.
Postmortem examinations were being carried out yesterday at Cork University Hospital. The deaths are being treated as tragic accidents.
William Hallihan, principal at Nagle Rice secondary school in Doneraile, said he had fond memories of past pupils David and Emma. A member of staff at the school met Emma last Saturday in Mallow and she excitedly told him of the interview she had lined up for a position at an accountancy firm in Cork.
"She was a very quiet girl - very gentle. She had a couple of very close friends in school and she went on to study accountancy at the Cork Institute of Technology. You wouldn't ever meet her without a smile on her face. It is terrible to see an entire family wiped out."
Mr Hallihan said David was also a gentle, quiet type of person who was a talented technical drawer, having receiving an A1 in the subject in his Leaving Certificate in 2000. He was also involved in hurling at school and at local level, and was working in the construction industry at the time of his death.
Tributes poured in yesterday for their mother, Ita, who was employed as a clerical officer at Fermoy Garda station. Inspector Pat McCarthy worked closely with Mrs Noonan during her eight years at the station and described her as a "tremendous worker" with a very bubbly personality.
Co-worker Supt Flor Horan of Fermoy said Mrs Noonan only moved to her new apartment in Castletownroche last week, with the family home having previously been in Freemount, Charleville.
The area where the accident took place is about a quarter of a mile from Mrs Noonan's new home.
Fr Pat Scanlan, parish priest in Castletownroche, said the community was still trying to come to terms with the enormity of the tragedy. He spent some time on Monday comforting the children's father, David Noonan, from Charleville, who was struggling to come to terms with losing three members of his immediate family.