ESTHER Lammertink was enjoying a family outing at a popular Sydney rock pool on a sunny Sunday when her daughter suddenly disappeared down a drain.

The 10-year-old’s horrific ordeal took place a busy public pool at Dee Why in the city’s north when her parents looked away for just 20 seconds.

One moment, Myrthe Koning was enjoying the water with her brother and then she was sucked into a hole which was concealed below the waves.

While her brother frantically looked for her, she was dragged through a sharp, rocky passage which sliced her open and dumped her in the ocean.

Her mother told news.com.au that her daughter was lucky to be alive and the terrifying incident had caught the whole family off-guard.

“It’s a very busy, public rock pool and there were lots of people in the water that day — there was even groups of nippers having lessons there.” she said.

“We live locally, so we come down often and look at the surfers in front of the rock pool,” she said. “When there’s big waves, there’s some kids who like to hang on to the chain and then when the wave comes they jump in the water and it creates waves in the water and that's what they like.

“We were there for about half an hour watching everybody in the rock pool and then my kids decided they wanted to have a go as well.

“We thought ‘the rock pool’s open, there’s so many kids, it should be OK’ so we decided to let them have a swim too.”

She told her husband they should keep an eye on the children because it was so busy and she didn’t want anybody to accidentally jump on them.

“We were watching the kids and then I looked away for about 20 seconds and when I turned around my son was panicked, walking up and down and looking in the rock pool,” she said.

“I could see that he was very anxious and upset about something so I started walking towards him and I saw my daughter popping up outside the rock pool — it was a weird thing.”

Fortunately there was a passer-by standing one metre away from the 10-year-old, who pulled her to safety with the help of another onlooker.

The youngster was then taken to hospital with several deep cuts and multiple grazes after the horror incident. Her cuts were glued together and she was given antibiotics.

Thankfully the young girl has now recovered, but the incident took the family by surprise.

“We didn’t even know that hole was there,” Ms Lammertink said. “A lifeguard came over, had a look in the water and then he saw it at bottom of the pool.”

She believes a freak combination of factors caused the dramatic incident, including a northerly swell, big waves and a strong undercurrent.

The concerned mother then reported the incident, which happened on February 18, to Northern Beaches Council.

She says the council has taken the incident extremely seriously and blocked the hole three weeks after the incident.

However, she wanted to share her daughter’s story so other parents are aware of the potential threat at other pools.

Northern Beaches Council’s General Manager Environment and Infrastructure manager, Ben Taylor told the Manly Daily: “This is an unfortunate and unusual incident and one Council is taking very seriously. I’m very glad to hear the young girl is OK and recovering well.

“Council has taken interim steps to close the opening while a grate is being fabricated to reduce all risk. Lifeguards are also continuing to monitor conditions and swimmers within the rock pool and undertake closure of the pool if required.”