Freediving is the latest craze that is a deadly trap if you are not aware of the dangers.
There are so many freedivers currently appearing in underwater videos and photos, people are jumping straight in without any instruction.
Last month in Queensland, a 19 year old and his three friends were competing to see who could dive the deepest. When he blacked out and sank in 30 metres of water, his friends brought him to the surface but he couldn't be revived.
The founder of international free diving body Apnea International, Erez Beautus said free divers should always have a "safety buddy" whose job it is to watch you all the time. "If we dive deeper than 10 metres, the sole responsibility of the safety diver is to take care of his buddy at that moment in time."
"It's very depressing to hear about young people that lose their lives and in my career as a free diver instructor, I've had a few to deal with."
"Since we are young and jumping in the water, in the pool, and trying to swim lengths underwater, - that's free diving - snorkelling, under-water photography, that's all free diving."
You can actually hold your breath for quite a long time, without any damage - it's quite a safe activity, to be honest."
"I think the press wants to tout it as an extreme sport, and we don't think it's that kind of sport at all" he said.
Tell that to 12 year old Jack McMillan's mother. Her son died from "underwater blackout" - doing underwater laps in his pool in 2013. He challenged himself to see how many he could do.
His mother said "He thought it was great, it was something he'd been doing over the Christmas holidays with friends and family in the pool. I looked back and saw him at the bottom of the shallow end, his knees were bent up in a foetal position and I thought - is he playing?"
But he wasn't.