Teen drowns at a popular lake in harrowing scenes as rescuers recall desperate attempts to save him

A teenage boy has drowned at a popular lake after he became stuck under a pontoon in front of horrified onlookers, including his family. 

Emergency services were called to Lake Leschenaultia in Chidlow in the Perth hills district on Tuesday afternoon after a swimmer struggling in the water failed to resurface. 

The teen's twin brother and mother alerted bystanders and emergency services after he failed to return to shore.

Up to 20 bystanders spent almost hour searching for the teen in the murky waters before police divers pulled his body to shore.

The boy was unable to be revived at the scene, despite the efforts of paramedics. 

Emerald McKelbie was among the first bystanders to jump into the water to try and locate the teen after hearing his brother's screams for help.

'The boy was yelling out, 'help, help ... he's under there' and then everyone started running in,' the mum-of-two recalled.

'We all just started taking turns and diving in ... we actually made a circle to make sure [we could find him].

A 17-year-old boy drowned at Lake Leschenaultia, east of Perth on Tuesday. Pictured are emergency workers at the scene

A 17-year-old boy drowned at Lake Leschenaultia, east of Perth on Tuesday. Pictured are emergency workers at the scene

The teen failed to surface after becoming trapped under the lake pontoon. Pictured are emergency workers at the scene

The teen failed to surface after becoming trapped under the lake pontoon. Pictured are emergency workers at the scene

'Everyone was just taking turns to dive in ... and we made sure we counted everyone's head, so if two people were going under water we knew that two people needed to come back up ... it was really good team work. 

'I was yelling to get paddle boards because at least you can stand up on paddle boards, but even then, the water was still too dark to see.

'We did everything but ... (the) boy didn't come back up.

'Everyone was shaken up, everyone was in tears in the end because we couldn't find him.' 

Another bystander Susi Asmara was learning how to swim when she heard a commotion of 'people screaming'.

'It's very sad, they're not my family, I don't know who they are, but I'm shaking,' she told The West Australian.

Emerald McKelbie (pictured) was among 20 bystanders who spent an hour searching for the teen in the water

Emerald McKelbie (pictured) was among 20 bystanders who spent an hour searching for the teen in the water

A heavy presence of emergency workers remained at the lake for the rest of the afternoon.

The lake was closed while the authorities carried out investigations.

Workers were seen pulling the lake's pontoon to shore shortly after the teen's body was found. 

'The death is being treated as non-suspicious and a report will be prepared for the Coroner,' a police statement read.

The teen's grieving family members were also seen consoling each other. 

Lake Leschenaultia is a former railway dam that was converted into a recreational waterway.

The popular spot is described by the local council online as 'the perfect spot for a family outing with cool shaded areas, lawns, white sand beaches and playground equipment'.

The latest tragedy comes a day after a man in his 40s drowned while trying to save two children caught in a rip in Bremer Bay on Monday.

It also takes Australia's summer drowning toll to 53 lives lost since December 1, one more than this time last year. 

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