Holly Nicholson drowned while trying to save her younger brother Sam from rough seas of a South Gippsland beach.

Emergency services minister Jane Garrett said there were "serious concerns" about the way emergency call taker ESTA handled the Nicholson family's triple-0 call.

She said the family called from an ambulance at around 8.20pm on Thursday, but it took about 24 minutes for paramedics to be dispatched and the ambulance did not arrive until 9.01pm.

Holly and her brother were swimming at Williamsons Beach near Wonthaggi just after 8pm on Thursday, when 11-year-old Sam got into trouble as the water became rough.

Sam was saved, but Holly soon got into trouble herself and the Year 8 student was pulled from the water unconscious.

Emergency services tried for more than an hour to revive her but she could not be resuscitated.

Ms Garrett has commissioned the Inspector General of Emergency Management to carry out an investigation into the tragedy.

"I'm very sad on behalf of the Victorian government and the community that the distress this family is going through is being added to by the fact we have to conduct this investigation," she said. "But I assure them that this investigation will be rigorous and thorough and will be done with great respect to the family. All the findings will be implemented."

Ms Garrett said ESTA and the coroner will also be carrying out their own separate investigations.

She said the loss of the "beautiful and brave 13-year-old" was a "deeply tragic day" for the state.

The principal of the school Holly attended also paid tribute to the Year 8 student.

Wonthaggi Secondary College principal Garry Dennis, said the 13-year-old was a "caring and gentle" student, whose loss would be felt across the community.

"She endeared herself quietly to all those around her - students and staff," Mr Dennis said.

"The huge impact she had in our school is being reflected in the response to the news that we have had today. We are all feeling the loss today and our thoughts are with her family.

"The school will do all it can to support family and friends."

Mr Dennis spoke to 20 of Holly's close friends on Friday morning, who remembered her as "kind and loving".

They described her as an "amazing friend", who was always helping others and who "always found a way to make everyone else feel good".

"[She would] light up anyone's day with just her smile," one friend said.

Others on Facebook paid tribute to the "brave girl".

"I was fortunate to have known her and the loss of her beautiful, warm smile and caring, happy and loving nature will be felt greatly but will live on in our memories," one friend wrote.

Another said: "You will be forever remembered a hero."

Holly's brother suffered minor injuries and was taken to the Monash Medical Centre, where he remained on Friday afternoon.

The siblings were at the beach for a family outing, a police spokesman said.

The family, from Dalyston, was swimming at the beach directly in front of the Wonthaggi desalination plant.

Wonthaggi police Sergeant Glenn Birt said the teenager's death would have a "huge impact on the community".

Sergeant Birt said the beach was mainly a surfing and fishing spot.

"Locals do swim in the shallows, but there is a strong undertow," he said.

Life Saving Victoria spokesman Paul Shannon said the beach was rated as "extremely hazardous" and was not patrolled.

"It's a straight-out tragedy that's happened to a family that's probably gone down to have a fun day at the beach," he told radio station 3AW.

"Our hearts just go out to this poor family who have lost a child and have another one in hospital.