People left with nightmares after man dives 65 feet into sea to prove the frightening reality of the ocean

A man took to the ocean to show how various depths can impact the human body underwater - and it's leaving people pretty terrified.

Free diving is one of those sports which is really, really not for the fainthearted.

And this clip which was shared on Reddit makes that disturbingly clear.

That's because of the impact of water pressure on the human body when you dive deeply.

Freediving can be a deadly sport (Sebnem Coskun/Anadolu via Getty Images)

The video explained: "If you descend only 10m into the ocean, you are subjected to another additional atmosphere of pressure: that’s twice as much pressure as you’ve been used to at the surface."

And, of course, the deeper you go, the more the pressure increases.

The clip explained: "And for every 10m beyond you get another atmosphere of pressure.

"That starts to manipulate your body, your anatomy and your physiology in quite profound ways, which actually make the endeavour of diving into the deep ocean uniquely difficult."

This includes that will 'compress you and shrink the air-containing spaces in your body'. It also changes how the gases in your body behave.

And Redditors were understandably disturbed and shared their thoughts in the comments on social media.

One wrote: "WHAT DO YOU MEAN YOU SINK WHEN YOU GO DEEPER WHAT THE F*CK"

Another posted: "I had no idea this was a thing and I just became slightly more afraid of the ocean."

A third commented: "Such a simple thing to give me nightmares."

"Well I wasn't scared of water before now I'm terrified thanks," a fourth person said.

The effect of pressure on the human body is also a huge factor in how scuba diving can work.

As you get deeper, the pressure means that your body is physically not strong enough to inflate your lungs - even if air is there.

The free diver gradually got lower and lower (Reddit)

According to DeeperBlue.com, every additional 10 meters you dive, the pressure on your body increases by 1 bar.

So as our volume decreases, the less buoyant we become.

To assist, you have your supply of air released under pressure, with the increased pressure actually giving your diaphragm a helping hand in inflating your lungs.

And as you go deeper, you need to release more pressure to counteract the additional weight.

However, because of consumption of nitrogen from compressed air at a particular depth, scuba divers are at risk of decompression sickness and also must exhale continuously as they ascend - else risk injuries to their lungs or even death.

All this means that recreational divers cannot go below 18 metres, as per Dive Newcastle, though technical divers can go much deeper.

I'm not sure why you'd want to go deeper anyway.