Police used fingerprints to identify him.
Na Nagara's report into the death said the post-mortem examination found nothing suspicious and no evidence Pearson had suffered any injuries before his death.
He did have a particularly high acetone level at the time he died, which could be from uncontrolled diabetes, a prolonged period of fasting, starving or exercise, or hypothermia.
"There is no evidence that assists in establishing with any certainty how Cory came to be in the water," the report said.
"As far as has been able to be established, there is nothing suspicious about the circumstances of Cory's death. He may have simply fallen into the water."
He was not incapacitated by drugs or alcohol at the time of his death.
"It would appear from his mother's recollection of Cory's experiences learning to swim that he was not a confident swimmer. It follow that he would have struggled to stay afloat and rescue himself once he found himself in the water. Any efforts he made would have been significantly impeded by the fact that he was fully clothed, including wearing shoes, when he was found."