Missing schoolboy's brother last to hear his cry for help

Four days after a schoolboy went missing in waters near Walpole, Western Australia, authorities are no closer to finding him.

It was revealed today that the eight-year-old's brother was the last to hear from him before his disappearance, recalling having heard his screams.

"He's in shock, he's traumatised," Superintendent Kim Travers said.

"The brother has heard him call out for help.

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"(He) heard his little brother call out for help and immediately rushed down the little track to the log but he couldn't see his brother.

"What he did see was the little blue plastic kayak lodged in the tree."

Shortly after the boy's disappearance, his father located his jumper "jammed under one of the rocks".

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A special robotic camera has been brought in to go where police cannot, with conditions underwater increasingly difficult.

The land search for the boy was called off yesterday afternoon, but divers have continued to scour the river today.

It was originally presumed the boy had gone missing while kayaking, but police say that nobody had actually seen the boy enter the water.

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Divers have faced challenging conditions underwater, with visibility extremely limited.

It was hoped conditions would improve today, with water levels decreasing.

However, police have said the chances of finding the boy alive have dwindled.