Thread by @POCGamer

Knowledge is power, so let's learn about how the underwater world works. I have a background as a Divemaster (PADI, SDI), Master Scuba Diver (PADI), Commerical Diver (SCUBA to 40m, Surface Supply to 30m), and as a Scientific Diver (CAUS). I also have my SVOP.

Pressure is measured in Bar, with one bar representing 1 Atmosphere of pressure. Pressure increases at depth at a rate of 1 Bar or Atmosphere per 10 metres. If you want to get super math-y about it you can, but 10m is close enough for the bulk of work and fun done underwater.

Most divers operate between 10m and 40m in depth. Going deeper than that requires additional decompression planning and often breathing mixtures that have reduced amounts of both oxygen and nitrogen. So they max out at around 5 atmospheres of pressure.

Technical divers, submersibles, and submarines operate deeper. Most people max out at 105m. Most subs can hit 450m as normal depth and max out near 900m. Specially built submersibles can go to 11000m, as James Cameron did. However, as you can imagine, that's a lot of pressure.

Now, the human body is weird. Our fluid filled everything makes us remarkably crush proof from atmospheric pressure. But there's a tonne of other things that happen at depth to a human not inside a pressurized unit. The deepest SCUBA dive in the world was only to 332m, and...

...while the descent only took 15 minutes, the ascent was a 13 hour 35 minute operation with multiple decompression stops using different breathing mixtures. And that doesn't even get into the equipment failures from exceeding depth limits and the multiple divers that helped.

So, when things go wrong underwater, they really go wrong. The ocean, and any body of water for that matter, is an alien environment we left millions of years ago and it is full of the bodies of the careless, impatient, prideful, ignorant, and those who were just unlucky.

When things go wrong diving, it's either equipment failure (which is never good), or a biological issue like nitrogen narcosis, oxygen toxicity, or decompression illness. Being underwater is as risky as it is fun, but with subs of any sort, things get riskier in different ways.

Subs have, broadly speaking, three "maximum" depths. There's the test operating depth, where the sub is happiest. Then there's maximum operating depth, usually 2x test depth. That's the Do not pass under any circumstances depth. Then there's collapse depth, or crush depth.

These aren't set in stone though, and wear on parts and the hull can affect a sub's characteristics. Naval engineering is a whole subfield of engineering design for a reason and isn't a place where "disruptive technologies" or non-standard ideas tend to thrive. Not because...

... they're innately conservative or against new concepts. It's because the ocean doesn't care about how you feel your idea is great, it either makes the grade or ends up in pieces on the surface or laying on the bottom. Yes, talented amateurs do come along, but they are rare.

And the really smart ones? They aim to meet or exceed industry standards. They get things checked out by independent inspectors. They check every safety box they reasonably can so that bad things like this don't happen.

“There hasn’t been an injury in the commercial sub industry in over 35 years. It’s obscenely safe because they have all these regulations. But it also hasn’t innovated or grown - because they have all these regulations.” ~ Stockton Rush, CEO of OceanGate, 2019.

This is not the attitude you approach the ocean with. 35 years and no injuries is a success story. And there have been innovations, and growth; just not the kind a billionaire CEO wants. So he cut every corner he could. Read it all here:

nytimes.com/2023/06/20/us/…

So anyways, to finish up, there's little margin for error underwater and safety is not optional. Diving and submersible operations have become safe because the options are counter to human life.