Indeed, the grandparent post is a pretty good summary of the takeaways you get from taking PADI’s enriched air nitrox course (which is a requirement if you ever want to dive with enriched air).
In the olden days this was tracked manually (the ratio of your depth to percentage of air and time under water) via so called “dive tables”. The purpose and output of the dive table is to determine the safe amount of time you could dive at a certain depth without risking narcosis.
As this is a sliding window based on multiple variables - and you are very rarely maintaining a constant depth as you dive - it’s of course annoying and less accurate to hand calculate this. Modern dive computers just seamlessly calculate it all for you nowadays.
Fun fact: those dive tables were created by the US Navy conducting experiments on its own divers, there was a real human cost to acquire that information.
Scuba diving is great. You don't have to do deep or risky dives to enjoy it. There's a ton of fun in diving around reefs 10m down.
That story is pretty wild. And relatable.
I got myself into a little trouble when I dove the Blue Hole 16 years ago. We were warned pretty heavily how many people have died doing it, so I went in with a healthy level of anxiety. It was my second dive where the dive plan was to go to 40m, which is the limit on regular air.
The descent was surreal. You have the wall of the crater on your side, but everything else is different shades of blue. Past about 10m, there's not really any wildlife to look at, just blue. We descended straight down, going in slow motion. As we went down the blues got gradually darker and deeper.
At probably the high 20s, I started to notice I could really see the surface clearly anymore, and I started to panic. My breath started racing and I started being annoyed by my regulator in my mouth, which is an unnatural feeling to being with. For maybe a minute, I debated whether I should try to get myself under control, or signal my dive instructor I wanted to ascend. Meanwhile, we were still drifting downward. I worried whether nitrogen narcosis might affect my judgment or ability to control my panic.
In the end, I decided not to be a hero. I gave my instructor the thumbs up to ascend, and we went through the orderly process of safety stops. When we got to the top I told her I explained I was feeling panicky (you can't really communicate anything nuanced below the surface), and then I spent the rest of my tank diving the first 10m, which was relaxing, and let me finish the day on a high note.
that comment is a classic and certainly entertaining, but there are multiple levels of safety to prevent something like this from happening, the first of which is the wall of tombstones that greets you when you arrive at that specific dive site. To end up in that situation means to have already made a number of big, big errors.
I remember the Blue Hole as one the best dives I made, and not even the scariest: that prize goes to the time I was in calm waters at 20 meters, and the pressure regulator just failed, leaving me without air from both mouthpieces. And that's why you have a buddy...
I don't think I've ever had anything fail on me diving, but I've been with people who have run out of air (my buddy was constantly using all his up), so having to breathe off someone else's tank isn't uncommon.
As I mentioned in my sibling comment, I did have a scary time on the Blue Hole. I think my other most nervous dives were:
- Pacific dive in Costa Rica in rough seas and surge. We suddenly had visibility drop to near zero when we hit the outflow current of a river. Definitely a lesson in how quick conditions can change.
- Cavern diving in a cenote in Mexico. Nothing weird happened, but we went kinda far in, and I get nervous in overhead environments.
Running out of gas or having to breathe off of someone else's tank is uncommon. Gas planning and monitoring is a fundamental skill that every diver needs to master just to get a basic open water certification. If your buddies aren't able to do this reliably then they need remedial training.
It's good to practice gas sharing as a contingency in case of equipment failure but actually running out is not acceptable.
same, blue hole is notorious because inexperienced divers get pressured into deep dives they haven't trained for by local guides looking to make a quick buck.
my scariest dive was when a 14 year old got separated from the group and thought it would be a good idea to continue his dive for 30 minutes.
