The teenager had an extremely close call when he found himself literally up against a whale in the water.
Connor Lyons was freediving with a friend off the Sunshine Coast in Queensland, on the east side of Australia.
The pair spotted a pod of whales about 200m (656ft) in the distance, before they disappeared from view.
But the situation took a very tense turn when the mammoth animals suddenly appeared right in front of them.
Whale video: A calf bellyflopped onto a freediver in Australia
Connor’s underwater camera was rolling when one of the whales, a calf, came up out of the water and then landed straight on top of him.
The huge mammal submerged with enough force to knock the teenager’s flipper off his foot.
Connor told ABC News: “I thought the baby calf was going to spear me out of the water, but luckily it shot up vertical just before it got to me.
“It landed right on my left leg, like on my fin, and knocked my fin off. It was crazy.”
Whale video: The calf surged upwards and on its way back down it hit the freediver
The whale calf bellyflopped right next to me
“It looked like slow motion when it was happening.
“They’re just so big, even when they look like they’re going slow, they’re going so fast.”
Connor said there were a few scary moments after the bellyflop due to the force of the whales.
He explained: “After they went past, after the calf bellyflopped right next to me, there were currents that kept us under for a second.
Whale video: The calf knocked the freediver’s flipper off his foot
“It was just the best experience, I’m going to remember this for the rest of my life.”
Two swimmers had the fright of their lives when they encountered a pod of whales in West Vancouver, Canada.
Video showed at least three killer whales zooming through the water at speed, charging straight at them.
The two swimmers scrambled out of the water onto rocks just in time to escape the approaching orcas.