Alby nearly drowned during a family holiday at Tuross Lake last week and Mr Jones and his wife Louise want to warn others to be ever vigilant while in unfamiliar surroundings.

The couple had taken Alby and his brother Odin, who turns three next week, to stay at a waterfront cabin at Tuross Lakeside Tourist Park on the Far South Coast.

But on Wednesday the little boys managed to unlock the sliding door of the cabin while they were getting ready in the adjoining bathroom.

"We thought we'd done everything right - we locked the door in the lounge area where they were watching television," Mr Jones said.

"I was in the shower and my wife was blowdrying her hair - we were literally in the bathroom for two minutes together before my wife went back into the lounge and found the kids gone."

Mrs Jones raced down to the nearby play area where she found Odin, but it was her husband who glanced out over the lake and saw their youngest child.

"When I saw Louise with Odin, I assumed Alby would have gone with him," Mr Jones said.

"So I turned around to go back inside, then took a quick look at the water and that's when I saw my young fellow floating in the water."

Mr Jones raced to the water's edge just 15 metres away and was at his child's side in seconds.

"I picked him up and all these little bubbles were coming out of his nose and mouth," he said.

"I thought the worst - I thought he was dead - but thankfully he was conscious and breathing.

"Another minute or so and he would have been gone."

Mr Jones wrapped Alby in a doona as he was turning blue and rang an ambulance. He was taken to Moruya Hospital and treated for hypothermia.

"Fortunately he was face up with the waves splashing over his face so he must have been getting some air," Mr Jones said.

"I credit the boys' swimming lessons, which they've been doing since six months. One of the things they teach them is to turn around and lie on their back in a starfish position if they fall in the water. And that's what Alby was doing."

The Royal Life Saving Society Australia advises parents to be extra vigilant during holidays, particularly in locations close to beaches, lakes, rivers and dams.

"Children need constant and active supervision when they're in, on or around the water,"its website says - something the Joneses know all too well.

"At home you've spent time child-proofing the house and securing the yard. On holiday, there's dangers and risks you're not aware of, so you need to take extra care, as we discovered."