I have a huge problem with how people gauge risks from scuba diving. This stems from the fact that IMHO must divers are horribly under trained and under practiced for what they are doing and usually are not following best safety practices. For those that are, I think diver is significantly less dangerous than other accepted activities (in fact, I’d be willing to bet that my drive to the dive is far higher risk than my dive).

Some examples of best practices that are not widely followed:

1. never rely on a dive buddy for air redundancy. If you are diving deeper (or longer) than you can perform a free emergency ascent safely, then you should have a redundant air source. “Two is one and one is none”. You might think that you can rely on your buddy, but unless they are literally within arms reach at all times, they are not a reliable redundancy source.

2. Skills must be practiced. When was the last time you shot a lift bag, did a valve drill, unplugged your inflator hose, manually inflated your BCD/wing, doffed your mask and donned your back up mask?

3. Do you know how to reliably navigate? How do you get back to the boat? Do you know how to safely run a reel without getting tangled up and while minimizing risk to the reel line? How about in 0 vis?

4. I love my computers but I plan out every dive manually and have a rough idea of what to do if both my computers fail. You do have redundant computers right? And you know how to use them right? I did almost 100 dives before I got my first computer. I think this is a good path since I have a solid understanding of what to expect from my computers.

5. Entry level training generally skips a lot of these safety tools and skills. I once dove at a Padi resort and brought a pony bottle with me. They dive operator didn’t even know what a pony bottle was. Do you think they are actually teaching about redundant air supply?

I’m certain that having all the right tools in your toolbox, practicing how to operate them and being mindful about how to use them significantly reduces risk.

I think diving is very dangerous for un(der)trained divers and I think the dive industry does a disservice by not portraying these risks and the need for more training/skills practice.

Frustratingly, my insurance says I’m more of a liability because I dive to 53m regularly (at least before kids) than the yahoo who only dives once or twice on vacation every few years to 20m. I dive to 53m with focused planning, training, and the right equipment explicitly so that I reduce risks. And I apply those same techniques to my shallower dives.

If you run out of air, ideally you're with your swim buddy and start breathing from their spare regulator and you make a safe ascent together.

I don't know why you're being down voted, but you're right.

A diver doesn't just "run out of air". A diver gets low on gas because they failed to look at their gauges, and/or didn't plan properly.

It can happen that you get a free flow on your regulator, inflator, valve or manifold, but none of these make you run out of gas immediately. You have time to swim to a team mate and breathe from their regulator (if you are on a single cylinder and can't close any valves).

If you have a valve rolling-shut (implying you're on a twinset), you _will_ run out of air until you open it again, and you would be trained to calmly open it, or just switch to your secondary regulator.

Running out of gas can be prevented by planning the dive and keeping an eye on your gauge, depth and timer.

You absolutely can just "run out of air". Equipment malfunctions happen.

Was on a dive where one of the girls hoses blew. She didn't remember her training and shot up to the surface - thankfully we were at ~5m already, but she still got the bends and they sent her to a decompression chamber.

Buddy was recently on a trip and had both his primary and secondary regs malfunctioned while deep. He was able to swim to his girlfriend, but he's been off-put from diving since then - and he's not inexperienced.

Having a buddy is nice, but honestly isn't reliable. Most of the time I'm joining a boat as a single, and while we have our group - it's really only the dive master that's paying attention to people. Everyone else is usually inexperienced or just doesn't even think to keep an eye on others because they're out on vacation.

And even when you do have a good dive buddy, you're not usually attached at the hip. Very often you're looking at something that intrigues you and your buddy gets bored to swim a few meters a way, etc. It'll happen 1000x times in a single dive.

I would still argue that no one ran "out of air" in any of those situations. They panicked and/or ignored their training.

The thing about diving equipment (especially regulators), is that they fail safe, meaning that they fail in a way that allows you to keep breathing.

When a regulator fails, it lets gas go. You can always breathe from it. The cylinder won't empty immediately, so you can get to your next gas source (your buddy, or your next gas switch depth) - cave/mine/wreck excluded.

> divers are trained to breath out during an emergency swimming ascent

To add a little more detail to this. You should ascend as slow as you can given the emergency situation but gently hum out your air rather than breath out. This slows it so you avoid the panic of empty lungs when not near the surface and also allows air to escape if it’s expanding quicker than you are humming :)

Instinctually (well, once you overcome the most naive instinct of holding your breath) one might think they need to exhale fast enough that the expansion of volume in the lungs doesn't outpace the rate of exhalation, but in reality even the slightest bit of intended exhalation will keep the airway open enough to prevent lung issues, right?

Yes, the point is to keep the airways open, but that’s hard to demonstrate hence the suggestion to “make a stream of small bubbles as you ascend”

That was what I was taught at least when I learned recreational diving.

Interesting concept… it seems diving is only about 1/4 as dangerous as the average other risks people take in a day, so it seems pretty inconsequential in overall risk unless you are a professional and dive multiple times daily for years on end, but I would guess a pro had less risk per dive due to skill.

Diving with a buddy (which you should absolutely always do) in good weather basically reduces risk to zero as long as you don't get too far away from each other. The chances of four regulators failing (two main, two octopuses) are close to nil.

…as long as you don’t penetrate a wreck, dive under ice, or dive in a cave. Since a roof severy decreases the chance to survive if something happens and you need to surface.

Also, of course, tech diving, typically below 40m, can also severely limit the ability to emergency ascend to the surface without injury.

Also as long as you keep a line straight to the surface. Cave diving and wreck diving are far, far more dangerous, and require special training. There are many ways to die if you can't just head straight up for oxygen in an emergency.

I strongly disagree that one should always dive with a buddy. But I’ll also say that one shouldn’t dive alone. Exit and entry are usually the most dangerous part of the dive.

Diving in low vis, spear fishing, or confined spaces don’t match with having a dive buddy. But they do match with redundant air supplies and other safety measures I mention in another comment.

Also unless your buddy is literally within arms reach at all times, they are not a redundant air source.