“My wife was completely panicking whilst this was happening and ended up shouting from the balcony which is not like her as she is very unconfrontational.

“I watched and whistled to get their attention but didn’t want to make the situation worse or into something it wasn’t… And in fairness, my daughter did manage to ‘swim’, and then walk to the shallow end where they collected her.”

Incredibly, this isn’t the first time such incidents have occurred with the children’s grandparents.

On one occasion, the father claims he walked in to find his infant son wandering halfway up the stairs.

Additionally, on a different day, he noticed his daughter’s car seat harness was far too loose because the grandparents didn’t know how to fasten it properly.

However, speaking on the swimming pool dilemma, he said: “When they returned they said: ‘One little girl safely returned’ and I said: ‘Yeah just about, you left her in the deep end’.

“They said: ‘No we didn’t’, and at that exact moment my son fell and hit his face on a table… I had to deal with that… how can I re-address this, am I overreacting?”

The anonymous post has since racked up hundreds of comments online, with countless users claiming this is a blaring red flag.

Concerned, one person warned: “Behaviour like this is an iceberg. You witnessed them in the pool, but unless you constantly spy on the parents with the granddaughter, then you aren’t seeing everything.”

Meanwhile, another said: “This particular time wasn’t a massive deal maybe but next time who knows what they’ll do.”