Best Comprehensive Book on Diving

[David Wilson]

My favourite diving book remains Your Guide to Underwater Adventure written by Peter Small and published by Lutterworth Press of London in 1957:

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As a contribution to diving literature, it is a timeless classic reminding us what it was like to "try out" underwater swimming in a decade when recreational diving was something entirely new and the films of Hans Hass and Jacques-Yves Cousteau drew people to the cinemas in their thousands.

Here's a "plate" from the slim volume, captioned, as you can see, "If underwater swimming is not fun, it's not anything":

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Peter Small's philosophy of underwater swimming is essentially mine too. Enjoyment is the key. It's how many of us began our love affair with the subaquatic world. The author, a journalist who knew how to write well, was an accomplished diver who later died tragically during an experimental deep descent widely reported in the newspapers at the time.

 

[old frogman]

I fondly remember those snorkels with the ping pong ball.

 

[David Wilson]

I fondly remember those snorkels with the ping pong ball.

So do I. My parents gave me that very Typhoon valved breathing tube as a birthday present when I was young. I no longer use it for breath-hold diving, but I do have some mid-twentieth-century ball- and float-valve snorkels and combination snorkel-masks in my collection of historical diving equipment. The latter were originally developed to serve the spearfishing community, who spent long periods face-down on the surface stalking their prey.

 

[USdiver1]

I fondly remember those snorkels with the ping pong ball.

I had one too. Never much of a fan, as the ping pong ball would jam due to evaporated salt sticking to it during long snorkels around coral reefs. Worked ok in cold fresh water, just nothing to see in a quarry.

 

[old frogman]

Is it actually called a safety stop in that manual? Pilmanis says the Doppler systems were widely available by 1971, so it would be interesting to know if the BSAC mention used Doppler data or just the empirical stopping that was going on. There seems to be no published studies prior to those of Pilmanis.

Just found my dust covered 1972 BSAC Manual. Page 488, Appendix 17. Decompression Tables, Hard Work - Use of Decompression Tables.

"... On all occasions when hard physical work is carried out by a diver the decompression routine for the dive is to be taken as that for the next longer time increment for the dive. Fin-swimming is rated as Hard Physical Work".

When you ascend you are decompressing, whether it is NDL dive or a dive requiring mandatory decompression.

Using BSAC//RN tables 1972, is you conduct a dive to 100 ft for 20 min (which does not require mandatory decompression), you use the next longer dive increment to 100 ft for 25 min. This longer dive increment requires a 5 min stop at 10 ft. In effect you are conducting a safety stop for a dive to 100 ft for 20 min.

The word safety stop does not appear in the text however at the time we referred to it as precautionary decompression.

I believe the US Navy tables had a similar procedure for hard work.

I believe that this procedure was in place well before the doppler ultrasound technology. At the time the existence of micro bubbles was a hypothesis based on observation of navy divers feeling tired after deep dives which suggested blood flow due to the presence of microbubbles.

Back then, I applied this procedure for deep dives and repetitive dives. It worked for me. Never got bent.

 

[tursiops]

Just found my dust covered 1972 BSAC Manual. Page 488, Appendix 17. Decompression Tables, Hard Work - Use of Decompression Tables.

"... On all occasions when hard physical work is carried out by a diver the decompression routine for the dive is to be taken as that for the next longer time increment for the dive. Fin-swimming is rated as Hard Physical Work".

When you ascend you are decompressing, whether it is NDL dive or a dive requiring mandatory decompression.

Using BSAC//RN tables 1972, is you conduct a dive to 100 ft for 20 min (which does not require mandatory decompression), you use the next longer dive increment to 100 ft for 25 min. This longer dive increment requires a 5 min stop at 10 ft. In effect you are conducting a safety stop for a dive to 100 ft for 20 min.

The word safety stop does not appear in the text however at the time we referred to it as precautionary decompression.

I believe the US Navy tables had a similar procedure for hard work.

I believe that this procedure was in place well before the doppler ultrasound technology. At the time the existence of micro bubbles was a hypothesis based on observation of navy divers feeling tired after deep dives which suggested blood flow due to the presence of microbubbles.

Back then, I applied this procedure for deep dives and repetitive dives. It worked for me. Never got bent.

Thank you for this detailed response and additional information.

I believe the term "safety stop" as used today is a different procedure, however, derived from different reasoning than those precautionary decompressions. they all have the same ultimate purpose, of course, but that does not mean they are the same.

I will continue to support the idea that today's "safety stops" for NDL dives arose from the Pilmanis work in the early 1970s.

[rant on] Today, an NDL dive is one that does not require mandatory decompressions stops. The fact that some decompression takes place during ascent is irrelevant. It is correct therefore to say, "all dives involve decompression." However, it is misleading -- perhaps disingenuous -- to say, therefore, "all dives are decompression dives." And quite wrong to say all dives are "deco dives" (which you did not say, of course) since that is now the shorthand for mandatory decompression stops. [rant over]

 

[USdiver1]

[rant on] Today, an NDL dive is one that does not require mandatory decompressions stops. The fact that some decompression takes place during ascent is irrelevant. It is correct therefore to say, "all dives involve decompression." However, it is misleading -- perhaps disingenuous -- to say, therefore, "all dives are decompression dives." And quite wrong to say all dives are "deco dives" (which you did not say, of course) since that is now the shorthand for mandatory decompression stops. [rant over]

Tru dat.

While conservative, the US Navy tables were explained to recreational divers as being developed for young men in top physical condition, and that a recreational diver should go one additional table increment when diving, similar to the BSAC practice noted above. Microbubbles or physical condition, whose to say the exact reason for the safety stop.

 

[old frogman]

Thank you for this detailed response and additional information.

I believe the term "safety stop" as used today is a different procedure, however, derived from different reasoning than those precautionary decompressions. they all have the same ultimate purpose, of course, but that does not mean they are the same.

I will continue to support the idea that today's "safety stops" for NDL dives arose from the Pilmanis work in the early 1970s.

[rant on] Today, an NDL dive is one that does not require mandatory decompressions stops. The fact that some decompression takes place during ascent is irrelevant. It is correct therefore to say, "all dives involve decompression." However, it is misleading -- perhaps disingenuous -- to say, therefore, "all dives are decompression dives." And quite wrong to say all dives are "deco dives" (which you did not say, of course) since that is now the shorthand for mandatory decompression stops. [rant over]

I generally agree with your response. However, I did not say all dives are decompression dives. What I said is that "when you ascend you are decompressing". You are ascending from a zone of higher ambient pressure to a zone of lower ambient pressure. Consequently, when you ascend gases dissolved in your tissue are decompressing.

We need to make a distinction between the word decompression (which may be continuous as when ascending) and the process called staged decompression (where you stop at a predetermined depth for a period of time).

 

[old frogman]

I generally agree with your response. However, I did not say all dives are decompression dives. What I said is that "when you ascend you are decompressing". You are ascending from a zone of higher ambient pressure to a zone of lower ambient pressure. Consequently, when you ascend gases dissolved in your tissue are decompressing.

We need to make a distinction between the word decompression (which may be continuous as when ascending) and the process called staged decompression (where you stop at a predetermined depth for a period of time).

Further to my last post, the introduction of the safety stop, by PADI and other training agencies, was a major step in the risk reduction of DCS. During the 1980s the safety stop was heavily emphasised to recreational divers by these training agencies. In contrast, the previous practice of using the next longer time increment with navy tables was not well communicated to recreational divers, for example, in the BSAC Manual 1972, it was literately buried in fine print in an appendix. In retrospect, it should have been written in bold text and placed in the book where it could not be missed.

 

[MarkA]

Further to my last post, the introduction of the safety stop, by PADI and other training agencies, was a major step in the risk reduction of DCS. During the 1980s the safety stop was heavily emphasised to recreational divers by these training agencies. In contrast, the previous practice of using the next longer time increment with navy tables was not well communicated to recreational divers, for example, in the BSAC Manual 1972, it was literately buried in fine print in an appendix. In retrospect, it should have been written in bold text and placed in the book where it could not be missed.

I learnt with BSAC in the 1980's and used the RNPL/BSAC tables. In the lecture it was certainly brought up about not pushing the tables and using the next increment. don't remember what the manual said. No mention of safety stops at this time. If I remember it was early 1990's before BSAC suggested a safety stop at 6m as this was the stop depth of the BSAC88 tables.

P.S. didn't realise there was an imperial version of these tables.