Dive Table Variances

[ystrout]

Hi Guys,

I'm new to this forum. Have been reading threads since I got back into diving this past summer, but wanted to ask a question so I made an account.

I did 2 dives yesterday out of San Diego. The first dive was at 44 feet for 42 minutes. I had an hour and 45 minutes of surface time, then did a wreck dive to 65 feet for 24 minutes. According to the PADI dive table that I have in my log book, I finished in the N group. After my surface time, I was in the B group. So my max bottom time at 66 feet (rounded to 70 feet) should be 31 minutes. All is good and well, or so I thought....

Then last night, I was messing around on the internet and came across the NAUI dive tables. I didn't even know about these. I only got back into diving a few months ago. But they're different than the PADI tables. According to the NAUI tables, I would be in G group after my first dive, then the E group after my second dive, which would leave me only 19 minutes of bottom time at 65 feet (rounded to 70 feet).

So my hypochondriac personality kicked in, and now I'm worried about DCI. Do you guys think I'm okay? I don't feel any different.... No achy joints or muscles. No rash. Some random itches on my body here or there, that's normal though. My rental Suunti Zoop Novo dive computer did say "STOP" by the depth marker the entire second dive, but I'm pretty sure that is signaling a safety stop. Went away after my safety stop. So do you guys think I fall into the safe, no decompression limits?

And one more question. Why do the two tables have variances? Which one is more accurate? Is my PADI one outdated? I got it 10 years ago, but it is still online.... Also, even though I was down for 42 minutes and 24 minutes, I did a 3 minute safety stop on each dives. And the descent/ascent took a couple minutes. So I'm not sure how to factor that in.

 

[PfcAJ]

Hi Guys,

I'm new to this forum. Have been reading threads since I got back into diving this past summer, but wanted to ask a question so I made an account.

I did 2 dives yesterday out of San Diego. The first dive was at 44 feet for 42 minutes. I had an hour and 45 minutes of surface time, then did a wreck dive to 65 feet for 24 minutes. According to the PADI dive table that I have in my log book, I finished in the N group. After my surface time, I was in the B group. So my max bottom time at 66 feet (rounded to 70 feet) should be 31 minutes. All is good and well, or so I thought....

Then last night, I was messing around on the internet and came across the NAUI dive tables. I didn't even know about these. I only got back into diving a few months ago. But they're different than the PADI tables. According to the NAUI tables, I would be in G group after my first dive, then the E group after my second dive, which would leave me only 19 minutes of bottom time at 65 feet (rounded to 70 feet).

So my hypochondriac personality kicked in, and now I'm worried about DCI. Do you guys think I'm okay? I don't feel any different.... No achy joints or muscles. No rash. Some random itches on my body here or there, that's normal though. My rental Suunti Zoop Novo dive computer did say "STOP" by the depth marker the entire second dive, but I'm pretty sure that is signaling a safety stop. Went away after my safety stop. So do you guys think I fall into the safe, no decompression limits?

And one more question. Why do the two tables have variances? Which one is more accurate? Is my PADI one outdated? I got it 10 years ago, but it is still online.... Also, even though I was down for 42 minutes and 24 minutes, I did a 3 minute safety stop on each dives. And the descent/ascent took a couple minutes. So I'm not sure how to factor that in.

If you feel fine then you’re fine.

Tables have differences because the assumptions behind their creation are not identical.

Don’t sweat it. Decompression is a fuzzy subject.

 

[tursiops]

You are fine. The NAUI tables (and many others) are based on U.S. Navy tables, which were/are designed for one long dive, probably working hard, and not really caring very much about a second (or third or fourth...) dive that same day. The PADI tables made different assumptions, aimed at being a little less generous with bottom time on the first dive, but more readily allowing for repetitive dives. There were tested extensively before being issued three decades ago. Many thousands of recreational dives have been made using those tables.

Some dive computers are based on the PADI tables, some are based on other assumptions and strategies. None of the dive computers or tables can guarantee your safety from DCS, but they all do a very good job.

P.S. (added) the safety stop is only "required" in a few situations, not relevant to your dives. Otherwise, it is just extra precaution. The ascent time is factored into the construction of the tables. Your "bottom time" is from the time you leave the surface until the time you leave the bottom, for tables. Many/most use their "submerged time" as their bottom time, which adds even more conservatism.

 

[BoltSnap]

Your "bottom time" is from the time you leave the surface until the time you leave the bottom, for tables.

Not sure where you get that from, but for NAUI, it is surface to surface excluding precautionary/safety/deco stop time.

 

[ystrout]

Thanks for the replies. Yaa I wasn't sure if DCI was one of those things you could have and not know. So every little itch or mild tingle on a random part of my body freaked me out! Lol. But that's good to know. I'll continue following my PADI tables the dive computer.

On a more positive note note, yesterday was my first kelp and wreck dives! Dove La Jolla Kelp first then the Ruby E (for all you San Diego folk), 35+ feet vis in the kelp, and 30 foot vis at the wreck.

 

[scubadada]

Welcome to decompression algorithms. The tables are different, the computers are different, they are all safe. Conservative to liberal, there is quite a difference in your NDLs,

 

[tursiops]

Not sure where you get that from, but for NAUI, it is surface to surface excluding precautionary/safety/deco stop time.

I thought the definition you provided was called Actual Dive Time (ADT) by NAUI, not Bottom Time.

The Navy defines it:

and PADI defines it:

and SDI/TDI defines it the same way, and so on.

If the NAUI tables are written in ADT, and it shows (say) 60 minutes for some depth, how do you know when to leave the bottom so you don't violate your NDL?

 

[PfcAJ]

I thought the definition you provided was called Actual Dive Time (ADT) by NAUI, not Bottom Time.

The Navy defines it:
View attachment 440801
and PADI defines it:

View attachment 440802
and SDI/TDI defines it the same way, and so on.

If the NAUI tables are written in ADT, and it shows (say) 60 minutes for some depth, how do you know when to leave the bottom so you don't violate your NDL?

30fpm from depth to safety stop.

Example (not actually looking at a table) So if you’re at 60’ you’d need to roll out at 58-59min.

But I mean we’re splittin some hairs here....

 

[tursiops]

30fpm from depth to safety stop.

Example (not actually looking at a table) So if you’re at 60’ you’d need to roll out at 58-59min.

But I mean we’re splittin some hairs here....

Yeah, I know HOW to do it, but you are asking recreational table-using divers to make calculations underwater. The brain stops working when it gets wet. What I don't see is why NAUI does this; what purpose does it serve? They even say in their materials they start with the Navy tables (where Bottom Time is clearly defined) and then modify them.

 

[Bob DBF]

Learn to read and use your computer properly, or use the dive tables, there is no accurate way to check one against the other.

I don't use that type of computer, but for the STOP by a depth, on mine I would find it it was indicating deco, a ceiling, and a mandatory stop on ascent.

If you use a computer, or tables, make sure you understand how to use it properly and what they are telling you. Otherwise you are diving by luck.


Bob