A FAMILY holiday at the dam has ended in extreme tragedy after two young girls were killed when the inflatable biscuit they were riding slammed into a submerged stump.
Tributes have been flowing for the 13-year-old and 14-year-old girls after the crash at Lake Keepit in Rushes Creek on Tuesday afternoon, which sent shockwaves through the local community.
The Leader has chosen not to publish details about the family or where they're from after police said they had requested privacy at this difficult time.
Oxley detectives were combing the scene on Wednesday as they work with specialist officers from the Marine Area Command to piece together what happened.
Oxley Superintendent Bruce Grassick told media they understood a speed boat had been towing an inflatable biscuit with the two girls on board about 4pm.
"Unfortunately as it went over a wake, the biscuit has propelled these children into a submerged stump," he said.
"The biscuit has actually collided with ... one of the submerged trees in the lake."
A 72-year-old man was driving the boat at the time and police confirmed he, and the two girls, were all related.
Superintendent Grassick said the extended family had been holidaying on the ski gardens side of Lake Keepit since before Christmas.
"We understand it's also a location they had been to before in the past," he said.
An observer was the only other person on board the speed boat at the time, and police believe at this stage the vessel itself did not strike anything.
Police said the driver was taken to hospital for mandatory testing and was not physically injured, but was "quite traumatised".
The area at the Ski Gardens Road caravan park was busy at the time and visitors rushed in their boats to help rescue the girls from the water and support the family, Superintendent Grassick said.
Members of the public tried desperately to save the teenagers and performed CPR while emergency services were called.
They could not be revived and sadly died at the scene, police confirmed.
Superintendent Grassick said witnesses were being interviewed as part of the police investigation, and items had been recovered for forensic testing.
"The boat was seized and will be subject to an examination, and the biscuit as well was also seized and will be subject to an examination," he said.
"We are trying to piece together exactly what has transpired on the water that day and that will take time.
"It's extremely tragic, what's happened at Lake Keepit."
Police, ambulance paramedics and the Westpac Rescue Helicopter Service were tasked to the scene on Tuesday.
A report will now be prepared for the coroner, who will investigate the circumstances surrounding the deaths.