My first deep dive

[Bazzathemammoth]

Hey all

I did my first dive below 30m in the weekend. We went to a local marine reserve and dropped on a pinnacle that rose up from 50ishm to 5m under the surface, with a few flat reef structures on the way up.

Aside from a choppy sea state it was amazing conditions with 16 deg (C) water and 20+m vis. We had large schools of fish swimming around us and some big yellowtail kingfish checking us out. It was a beautiful dive.

One thing that suprised me was how narced i got. Ive done plenty of diving in the 20-30m range and felt some mild narcosis, where my memory and time tracking is a little off. This time i went to 39m and I felt almost warm (for want of a better word) and my dive buddy had to remind me to check my instruments. This suprised me as i am normally really ocd about checking ndl depth and gas. My dive buddy is an instructor so i was happy to be pushing my limits with him.

I feel like i have a newfound respect for the risks of narcosis and why rec limit is at 40m. What has your narcosis experience been like at these depths?

 

[Raphus]

After 30m I really feel strong narcosis.
The difference between 30 and 40m is huge.

I had a 40m dive where I felt warm. Like really warm. Water temp was 4 degree..

 

[tbone1004]

Narcosis is different for everyone, and even for a specific person it is different for almost every dive and condition. You can go to 50m on air in a clear drift dive and be fine, and then get narc'd off your gourd in 30m when you're kicking. CO2 narcosis is something that is not usually talked about, but since CO2 is 25x as narcotic as nitrogen and oxygen, CO2 retention causes all sorts of problems in divers. The deeper you go, the more dense the gas is which leads to CO2 retention and subsequently CO2 narcosis.
If you were doing any kicking at all, or any sort of skip breathing the CO2 building up in your system likely caused that issue and it happens really fast...

 

[Brett Hatch]

At home in cold water (~10C), I've felt a bit narced in as little as 90' / 28m. 130' / 40m in cold water feels like I just slammed 3 liters of beer and then hopped into the driver's seat of a vehicle I don't know how to drive. Same depth in warm water feels kinda nice . It all depends.

Sounds like your take-home idea is to treat those deeper depths with the respect they deserve, and to maintain an awareness of your own narcotic state. Which is the right track to be on

 

[Bazzathemammoth]

Cheers for the info everyone. I think @tbone1004 is on the money, i was finning a fair bit to keep up with my buddy.

This article is interesting, i wonder if the warmth i felt was due to point 4 about blood vessel expansion as a reaction to co2 build up. What’s All the Fuss about CO2 in Breathing Gas? - Shearwater Research

I think next time ill talk to my buddy about slowing down a bit and see how i go. I can normally feel a build up of co2 while diving, and when i do i normally stop and take slow deep breaths until it goes away. I was probably a bit distracted to notice it on this dive.

 

[Brett Hatch]

That's a great article from Shearwater, thanks for sharing @Bazzathemammoth

 

[Bob DBF]

I think next time ill talk to my buddy about slowing down a bit and see how i go. I can normally feel a build up of co2 while diving, and when i do i normally stop and take slow deep breaths until it goes away. I was probably a bit distracted to notice it on this dive.

And/or breathe more, I have a less than optimal sac rate because I use the air I need. If I am working, I use the air I need to keep my CO2 down, it may not be efficient, but a CO2 hit can be devastating, more so when deep.

 

[Bazzathemammoth]

Thanks for that bob. I think the biggest issue was speed as i normally purge co2 quickly if i notice a buildup. My buddy is a very fit 20 something and he was wanting to explore as much of the pinnacle as we could down to 40m, so we were both pushing ourselves a fair bit. Im mid 30s and not as fit. In hindsight i probably should have just slowed down and not tried so hard to keep up with him.

According to my charts, i reckon we covered around 800m-1km (1/2 mileish) over the course of our 45 min dive and that includes a few stops to see some of the sights. Its an exposed site 20NM offshore and one that is usually hammered by the prevailing conditions. There was definitely a bit of fomo going on to make us want to see as much as possible.

 

[Wibble]

See if you can do a recompression chamber 'dive'. Did one with 8 people to 40m. Amazing how off your face you are at 40m. Giggling like schoolgirls and higher brain functions are considerably impaired.

Which is why we fall back on training and muscle memory.

Regularly dive well beyond this nowadays, always with some helium to keep the narcosis at bay and allow me to remember the dive.

 

[100days-a-year]

As has been mentioned tolerance is variable between individual divers and varies on a single diver.
To help cut down CO2 .
I wore the simplest low drag BC possible which was a BP/W with a small donut wing.
I would use the best breathing , highest flowing reg available.
I wore long freediving fins which are more efficient at low kicking rates. We would relate our speed and demeanor U/W as like a manatee or sea turtle.
This also had the secondary effect of not spooking the sealife as you are less perceived as a predator.
Personal tolerance is personal, that warm feeling for me started around 50m most days and was really noticeable at 60m when it was warm and clear. Winter diving in more constrictive wetsuits and colder darker water it would be more noticeable stsrting around 40m.