Dive Table Comparisons

Since I took my OW training through SSI and the dive table I first learn to use was the SSI table, I have been using the SSI dive table out of habit, even when my other certifications is PADI. My regular dive buddies uses the PADI table or the Norwegian Standard table, during dive planning I observed that the other divers usually required shorter SI between dives and allowed longer NDL times than my SSI dive table would allow.

That made me curious so I went online with my trusty visa card and bought a copy of the most used dive tables in my area to compare them and find the table that suits me better (less conservative than the SSI table), so today the mail-man delivered a little package with the PADI, US Navy and Norwegian Standard tables, and now it was time to compare with 5 test cases for NDL and 5 test cases for SI.


My initial bias was that there would be two pairs of similar results SSI + PADI and US Navy + Norwegian standard when comparing NDL and SI.


I was a bit surprised by the result, seeing that Norwegian standard was the second most conservative table and that PADI was the second least conservative one.

Test case 1 NDL:
First dive: 22 meters - 30 min
Second dive: 18 metes
First dive: 18 meters - 40 min
Second dive: 12 meters
First dive: 35 meters - 10 min
Second dive: 10 meters
First dive: 12 meters - 30 min
Second dive: 30 meters
First dive: 25 meters - 20 min
Second dive: 22 meters

Test case 2 SI:
First dive: 25 meters - 25 min
Second dive: 18 meters - 45 min
First dive: 30 meters - 17 min
Second dive: 22 meters - 30 min
* can’t do it as a repetitiv dive

First dive: 15 meters - 70 min
Second dive: 24 meters - 20 min
First dive: 33 meters - 14 min
Second dive: 12 meters - 100 min
First dive: 21 meters - 40 min
Second dive: 20 meters - 30 min
So the sorted list, based on this data, of diving tables from least to most conservative is:

1. US Navy
2. PADI
3. Norwegian Standard table
4. SSI

So I guess I’ll be diving with the PADI table from now on.

So is my test cases flawed? Should I test for other scenarios / metrics? Did I just waste my time and money? And why the big differences in minimum SI?

I struggled with your post - I can't tell if you are serious or just looking for a discussion. So for now I will pretend you are serious.

Why are conservative tables a bad thing in a cold water environment? You have less than 100 dives - isn't it better to be cautious early in your diving experience? With more dive experience in cold water if you want the more aggressive tables can't decide later - why do you need it now?

Seems like you may be playing with something you don't quite understand... Seems to me you would be better off diving with the tables you learned with and start asking questions to those that dive in your environment first before you declare you will change your training tables because it does not suit your arbitrary needs for right now.

Basking Ridge Diver:

I struggled with your post - I can't tell if you are serious or just looking for a discussion. So for now I will pretend you are serious.

Why are conservative tables a bad thing in a cold water environment? You have less than 100 dives - isn't it better to be cautious early in your diving experience? With more dive experience in cold water if you want the more aggressive tables can't decide later - why do you need it now?

Seems like you may be playing with something you don't quite understand... Seems to me you would be better off diving with the tables you learned with and start asking questions to those that dive in your environment first before you declare you will change your training tables because it does not suit your arbitrary needs for right now.

Click to expand...

The biggest problem I have is the SI, with the SSI I am most often restricted to one dive on a work day afternoon, with the PADI I can manage two. Also I was thinking that since most recreational divers uses the PADI table, it would be fine for me too ("Suits my needs" was maybe wrong wording?). I am also genuinely curious about what makes for those big differences, I would believe that they are created by somewhat the same or related data set, maybe by try and error in a chamber or by extracting values from an algorithm?

And I didn't say that conservative tables was a bad thing, but would think that PADI already have a good amount of safety margin.

Why did you take the SSI course? I am only curious what made you choose that organization?

When I think PADI I think Warm Water / Vacation diving - I don't think of Norway or the ocean off the NJ shore lately...
Do you dive with a PDC? If you do - do you follow your computer or your dive tables?

If you want to dig a bit more in the math that are behind those tables, I highly recommend you the book "The physics of scuba diving" by Marlow Andersen.It is a very simple book and I hope you'll be able to better understand the result you've got.

Basking Ridge Diver:

Why did you take the SSI course? I am only curious what made you choose that organization?

When I think PADI I think Warm Water / Vacation diving - I don't think of Norway or the ocean off the NJ shore lately...
Do you dive with a PDC? If you do - do you follow your computer or your dive tables?

Click to expand...

PADI is what my local dive school teaches. I dive with a computer, but plans my dives with my dive table and follows the plan under water.

exposure:

If you want to dig a bit more in the math that are behind those tables, I highly recommend you the book "The physics of scuba diving" by Marlow Andersen.It is a very simple book and I hope you'll be able to better understand the result you've got.

Click to expand...

Thanks for the recommendation, e-book bought.

Where did you find the e book? Do you have a link?

Jim Lapenta:

Where did you find the e book? Do you have a link?

Click to expand...

found it on an norwegian online book shop (Bokklubben), still waiting for the download link though.
Also aviable from Lybrary.com

Back when PADI did the research that led to its tables, the U.S. Navy tables were what most people were using. They used the 120 minute compartment as the controlling compartment for surface intervals. There was frankly not a lot of research that went into making that decision. This led to very long surface intervals, which made it difficult to plan a dive day. PADI reasoned that recreational divers did different kinds of dives than the U.S. Navy did, and wondered if the 120 minute compartment was appropriate for those dives. They did very extensive research using Doppler bubble imaging to detect bubble formation in blood, I believe for the first time.

The results of their research indicated that for most recreational diving, the compartment controlling surface intervals should be the 40 minute compartment. Wanting to add a level of conservatism to be safe, they made the 60 minute compartment the basis for surface intervals in their tables. That still gave them considerably shorter surface intervals than on the old Navy tables. To add an even greater level of conservatism, they made the first dive NDLs shorter. This gave recreational divers the length dives they wanted to do on the first dive while giving them shorter surface intervals before the second dive.

The exception comes on a multi-dive day when the divers are getting near the NDLs. In those cases, a longer surface intervals is appropriate, and that is why the PADI tables have the WX and YZ rules.

I do not know anything about the SSI tables.