Two lifeguards were on duty at the Queensland pool where a three-year-old girl drowned on the weekend.
The girl was at a family gathering at Logan's Bethania Aquatic Centre on Sunday when she was found floating face down in the 25-metre pool.
She died in hospital despite the efforts of lifeguards and paramedics to revive her.
Logan City Council, which runs the pool, said two lifeguards were watching over 50 people who were at the pool - one more than Royal Lifesaving Guidelines recommend for a crowd of that size.
All systems and procedures at the pool are now the subject of a detailed investigation, the council said in a statement on Monday.
Counselling has been offered to pool staff, and the council has expressed its sympathies to the girl's family.
Witness Mandy Strong said the tragedy happened very quickly.
"I just wish one of us that was there saw her jump in. I feel so sad for her and her family. They were playing with their kids the whole time," she wrote on Facebook.
Three other children were taken to hospital on Sunday after two other incidents at Queensland pools.
A 10-year-old girl was found unresponsive in a private pool at Caloundra on the Sunshine Coast. She was taken to the Caloundra Hospital in a critical condition.
And two boys, aged three and four, came close to drowning at a private pool in the south Brisbane suburb of Rochedale.
They were taken to Brisbane's Lady Cilento Children's Hospital in a stable condition.
