Feedback on recent two-tank and dive limits

[lizzzzz]

Hi all,

I’d appreciate feedback on my recent two-tank dive (see images). My Shearwater Peregrine was giving warnings about NDL=1 at end of second dive and put me into a 5 minute safety stop for the first time. Dive guide assured me we were within safe limits, but looking back I’m not so sure.

Dive 1: 45 minutes, max depth of 68.8’, and avg dept of 52’.

Dive 2: 53 minutes, max depth of 69.7, and avg depth 45.

Admittedly I was distracted by bad viz and shifting currents, as well as keeping close tabs on my teenage son/buddy, and not as focused on depth and time as usual. I did not clock until later that our SI was only 34-35 minutes. I know the Shearwaters skew conservative and initially dismissed the buzzing computer for that, but have been kicking myself ever since. Dive guide was with only my buddy and me and appeared (and self-described) as laser focused on safety, but in retrospect this feels dodgy.

Would appreciate input from those in the know so that I can have a clearer assessment of how risky this was. Thank you!

 

[grantmac]

Without knowing your gradient factors it's impossible to say

 

[Divin'Papaw]

I know the Shearwaters skew conservative and initially dismissed the buzzing computer for that, but have been kicking myself ever since.

They do not skew conservative. They follow the gradient factors you set. What are your GF settings?

 

[lizzzzz]

I should clarify: I’ve read that their default settings skew conservative and have been on several dives where everyone dove the same profile and only my buddy and I (both with same computer) got NDL warnings.

That said, I just checked and my current settings are as follows:

Conservativism: medium (GF 40/85)
Safety stop: set to “adapt”

 

[jborg]

Looking at the graphs you surfaced with a GF of about 50%. You're fine.

 

[inquis]

Looks like you surfaced with a gradient factor of about 55% on both dives. That's well under even the high-conservatism default. Not an issue in my book.

 

[Divin'Papaw]

I should clarify: it’s on the default settings, which I believe are more conservative.

Which are?

My advice is to learn what the GFs mean and then set them based upon your risk factors and temperament. Then once set, simply follow them.

If you have adaptive SS turned on, you will always get a 5 min SS if your NDL drops below 5 min or if you dive below 100’.

 

[lizzzzz]

Thanks, all! I hadn’t had this happen before even with deeper depths, but it’s perfectly possible I shifted my computer settings since then because it’s been a few years. (I’ve been diving with my son since last year, so much shallower and easier than previous years with friends.) I revisited the tables but wanted to check with folks here, since you all are a wealth of knowledge.

I think my biggest lesson is that I’m not ready to be in more challenging conditions with my kiddo-as-buddy. He had a great dive, but it made me a touch more anxious than needed. Good reminder to refresh myself on the basics of dive planning rather than relying too much on my computer - for my own peace of mind as much as anything else. Thanks again!

 

[34109411]

Which are?

My advice is to learn what the GFs mean and then set them based upon your risk factors and temperament. Then once set, simply follow them.

If you have adaptive SS turned on, you will always get a 5 min SS if your NDL drops below 5 min or if you dive below 100’.

yup

 

[Scared Silly]

I did not clock until later that our SI was only 34-35 minutes.

Therein lies your issue as to why the NDL was at one point 1 minute. All other setting aside, 35 minutes is a short surface interval. Why the rush to get back in the water?

Most divers plan for a 1 hour surface interval. Why? besides being a round number, it gives many tissues just enough time that the loading on the second dive does not run into a NDL. Even if diving to a similar depth.