Saturation divers are specialized workers doing construction or demolition hundreds of feet below the water's surface. This detailed report gives a sense of what it's like to have a grueling routine where a tiny mistake could mean a quick and painful death.
Saturation refers to the mixed gas required for breathing at such depths, like a mix of helium and oxygen called heliox, which has a funny unintended side effect. Via Atlas Obscura:
Saturation divers breathe heliox for the entire time they are in storage. And this brings us back to those final family phone calls. Helium is about seven times lighter than air, and sound waves travel much more quickly through it. The result is that buff, often ex-military men performing deadly serious jobs end up sounding like cartoon characters—and not just for a few moments, but for weeks on end. In the unfortunately named BBC series Real Men, a saturation diver in storage calls his son to wish him a happy birthday. "It's hard to understand my dad because he talks in a duck language," the boy says later, "and I don't speak duck."
The divers and their support teams adjust pretty quickly to the vocal distortion, but it can still make communication tricky—especially when accents are involved. "A helium Geordie [a native of Newcastle] from the northeast of England in a team with a South African and a Belgian makes communicating quite a challenge," Tweddle says. Tweddle, an affable, 39-year-old former police diver with a shaved head that takes on a gray cast by the end of a job, is the Geordie in the above scenario. Support vessels are usually equipped with a kind of descrambler for when the divers need to be in constant communication with the onboard support team, but the equipment is notoriously unreliable, and many dive supervisors choose not to use it.
Here's a short clip with footage of saturation divers at work:
• The Weird, Dangerous, Isolated Life of the Saturation Diver (Atlas Obscura)