Deeper dives first?

[Crass3000]

I think most people have been taught to make your deeper dives first and then do the shallower dives. It seems everybody I have spoke with seems to agree with this. However, when reading 'Deco for Diver's' the author mentions there is no evidence to back that claim up according to all the papers, books, etc that he had used as research. Do you really need to do deeper dives first?

Edit: To clarify I am talking about recreational depths but I don't recall if the author made that distinction.

 

[gekodivebali]

Nope there is no evidence beyond what is said in the PADI Open Water manual. DAN has refuted this myth in an article.

 

[dlofting]

Does anyone know where this "rule" came from ??

My only thought is that doing your deeper dive first allows more time at your max depth, since you have no residual nitrogen loading. Does this allow more time to work through any problems at depth and still avoid a decompression obligation......or is it just a safety "buffer" that was considered good practice before computers gave us much more accurate dive profiles ?

 

[gekodivebali]

Came from the PADI Open Water manual methinks. Interesting that the info is not repeated elsewhere in the curriculum, and remarkably so not in the technical diving courses...

 

[Bob DBF]

Does anyone know where this "rule" came from ??

My only thought is that doing your deeper dive first allows more time at your max depth, since you have no residual nitrogen loading. Does this allow more time to work through any problems at depth and still avoid a decompression obligation......or is it just a safety "buffer" that was considered good practice before computers gave us much more accurate dive profiles ?

In the 1980 PADI OW manual it suggests doing the deeper dive first to allow the maximum time at depth. It however did not have any admonition about doing dives in any order you choose.

In the 1963 "The New Science of SCUBA and Skin Diving", which I trained with initially, had nothing about it at all. It became evident while doing dive planning that you had more bottom time when doing the deepest dive first.

Sounds like this rule had a basis in fact, but has lasted longer than the knowledge surrounding it is taught.



Bob
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A nod, you know, is as good as a wink to a blind horse.

 

[tplyons]

My only thought is that doing your deeper dive first allows more time at your max depth, since you have no residual nitrogen loading. Does this allow more time to work through any problems at depth and still avoid a decompression obligation

This is how I understand the "rule"

 

[Damselfish]

The reason given for this when I got certified in 1990 was that when working the tables for the same 2 dives, you would get more BT with the deeper dive first. So this was seen a good thing for that reason. I think this was interpreted by many that it must therefore be a more conservative or safer way to go, and it took on a life of its own. Even though ops aren't quite as hung up on it in general as you used to see, it's still seems pretty engrained in dive schedules and briefings.

I did run into a place once where they had taken the refuting of the "deepest dive first" thing to heart, and interpreted it to mean it also didn't matter on a single dive - often starting dives shallow and ending deep. Sigh.