Mr Crook said Alex and his friends had been standing in the water at waist height, before moving into part of the lake which dropped off steeply.
He said there were no warning signs and life-saving equipment in the area where Alex was pulled from the water.
Mr Cook, 45, said he and his family wanted to spare other families the heartache they had to endure.
He said “our world got turned upside down” by the death of Alex, who had just been made a school prefect.
“We’re keeping busy with the start of our campaign,” he said.
“We are focusing on that and determined to make it safer – not just at Scotsman’s Flash but at every place with open water.”
He said: “Scotsman’s Flash is our first port of call but we are not stopping there.
“We don’t want any other family to go through what we will continue to go through.”
