ITV News Meridian reporter Sally Simmonds follows a day in the life of a saturation diver
For months at a time, a crew of four Portsmouth men carry out what’s considered to be one of the most dangerous jobs in the world.
The ‘saturation divers’ can spend months at a time working on the seafloor, 100 metres deep.
But the North Sea denizens of the deep have found a touching reason to resurface.,
The team are planning to row the Atlantic in aid of the Wessex Cancer Trust, in tribute to member James Piper's wife Nikki's brave cancer fight.
His friends and fellow divers Andy Taw, Lewis Locke and Chris Ayres have joined him to form the Bubbleheads crew for the Talisker Whisky Atlantic Rowing Challenge.
The four will be bunking down in a confined space as they make the challenging crossing in a tiny row boat.
But both tight spaces and holding each others' lives in their hands is all in a day's work for the crew.
ITV News Meridian followed the team on their gruelling work days as they trained for their row for charity.
Saturation diving is an extremely specialised profession, which requires practitioners acclimatise to deep sea pressure for long periods of time.
They prepare by living in a specially pressurised environment on or under water, before taking the daring dives.
They ready their bodies for the missions by breathing a helium-oxygen mixture - giving their voices the hallmark high and squeaky pitch before a dive.
The skill means they can work at great depths and reduce the time needed for decompression - and reduce their risk of the dreaded ‘bends’ sickness.
The divers tell how they cab live at depths of 100metres or more for up to 28 days.
Being a saturation diver requires achieving peak physical condition and the mental strength to endure lonely and challenging subsea conditions.
They must be prepared to drop everything to go to work - sometimes with as little as 24 hours notice - and carry out the tough job far away from family and friends.
Mr Piper describes it as a “difficult” and isolating job.
“Once you commit to saturation you're committed for a month and you can't really come out very easily. It’s maybe a five-day decompression."
Bellman Andy Taw demonstrates how he holds diver Lewis’ umbilical apparatus as his pal swims to start work more than 400ft beneath the North Sea’s surface.
“But that's actually really good visibility, because a lot of the time you can only see maybe a metre, two metres in front of you.
Lewis Locke adds: “Sometimes it’s worse. Sometimes when you're working on the seabed - if it's mud - you can be working in no visibility whatsoever.
It's not for everyone, Mr Taw admits
“They say it's quicker to get back from the moon than from 150 metres."