THIS is the heartstopping moment a six-year-old drowns in a pool as his cousin watches on helplessly – before a bystander bravely intervenes.

Startling footage captured the moment when the boy struggled to keep himself above water for almost two minutes, before a quick-thinking stranger jumped into action, diving in to save him.

The harrowing video begins with the two cousins standing on the side of a Fort Lauderdale pool in Florida.

The six-year-old boy named Oscar then decides to jump recklessly onto a blue inflatable sunbed.

He suddenly loses his balance, and then falls into the water.

Seemingly unable to swim, he starts wailing his arms around desperately, failing to tread water.

Standing on the side of the pool, his cousin realises he can’t do anything as he does not know how to swim either.

Desperate to help his drowning relative, the adult cousin tries dipping his feat in the water, in an attempt to get himself into the water too.

But he hesitates a few times when he realises he would also end up drowning.

He even tries to push out the sunbed for the child to grab on to.

But still struggling, the child takes no notice if the inflatable and continues to flail around in the water.

The youngster even appears to remain under the surface of the water for an extended amount of time.

He is trapped without air for over a minute and a half before someone comes to his rescue.

Luckily construction worker Roque Ivan Ocampo who was at the same building heard the screams and was alerted to the commotion.

He rushed into the pool area through a gate, before jumping in without any hesitation.

The heroic worker dragged the child to the side of the pool, before starting CPR.

Police are then seen arriving at the poolside, also helping the boy who luckily survived the frightening ordeal.

Ocampo told NBC News: “He doesn’t move at all, that’s why I thought maybe, ‘He’s dead,’ because he wasn’t moving.”

He also said in the moment there was “no time to think, just to act”.

The boy was rushed to hospital and is expected to make a full recovery.

Police officer Jamie Bodine stated: “It takes immense courage to do what he did, and I believe Oscar’s situation could have been much more dire if [he] hadn’t dived into the pool, pulled him to safety, and performed CPR immediately.

“I don’t think we thanked him enough that day.”

The boy and Ocampo reunited the next day, where he told Oscar: “You’re very strong and I’m so proud of you.”

But the internet was somewhat confused by the footage – especially the bizarre fact his cousin stood by for so long without doing anything.

One user said: “Where were the parents? Why were [they] left alone near the pool without supervision?

“Something is wrong with this scenario.”

Another said: “What a hero. That’s a real lifeguard! For that ‘cousin,’ why do you have a pool when you can’t swim?

“Why are you even standing there?”