How to get Bent

[Mike]

Just so you know I'm a 'vacation diver' too. I live in Colorado and have no desire to dive in lakes or quarries here so all my diving is done while on vacation. My diving will never be on par with peers who dive all the time, simply because of the nature of the skills get rusty between vacations, mind having to get back into diving mode, remembering how to assemble equipment etc... I compensate with some techniques that I try to adhere to. Try to schedule simple dives for the first dives in a series on vacation. Leave the video camera or still camera on the boat on the first couple of dives so I can concentrate on knocking the rust off the dive skills and keep a better eye on my buddy. Maintain tight buddy skills at all times during dives.

Interesting. I thought that was odd too but the dive company, who I thought in every respect (though I obviously have limited knowledge) was excellent, seemed to think nothing of sending people up on their own. Your response makes me think I was right in thinking that was weird.

Two red flags to me about the dive company you used were them splitting buddy pairs up, sending you up alone at the end of the dive and that they had no idea about your lack of time between dives. That last one is a big, big red flag. Saba isn't exactly known for timid dives and dive sites, maybe there are some that are easier and safer than others and hopefully those were the ones they took you to.

 

[rhwestfall]

The next day I get on the boat and we do a multilevel dive down to about 80 feet at max depth, gradually ascending throughout the dive to maybe 40 feet before surfacing.

Interesting first dive (depth) after an admitted 10 year absence..... can you honestly say you were prepared?

 

[Searcaigh]

interesting story, I seriously wonder why the dive operator did not ask you when you last dived, most places I have traveled to always ask "when was your last dive?"

With my local dive operator, they insist on a refresher if a diver has not dived for 18 months or more

 

[tlj3071]

Hello - my name is Tom, and I'm a vacation diver...

Working 70-80 hours/week in a location that is far enough removed from the ocean (or any lakes/quarries I'd want to dive in), means that I only get to dive on vacations - i.e. once or twice a year. However, I do try to keep my skills up by diving at least once every month in a local LDS's pool. Am I as sharp as when I completed my AOW? Maybe, maybe not, maybe more so, because I think about diving a lot, and try to simulate - in my mind's eye - various problem scenarios.

Tom

 

[TSandM]

Tom, I suspect we would fret far less about "vacation divers" if they took your approach. It's the people with the long surface intervals who occasion concern, as the original post in this thread illustrates.

 

[drrich2]

Pdxgal:

It's worth mentioning that TS&M helps train divers in OW courses, if memory serves, and coupled with the effort she's shown to help others grow as divers on the forum, I believe she's one of those seasoned people who's used to looking out for other divers (at least her student classes).

While one might expect newly certified, very occasional vacation divers & others apt to be new or rusty to dive safely & responsibly within their limits, it can be tough to do. Some don't know their limits yet, some are surprised at how rusty they are, and even fairly seasoned divers are often surprised at how much impact different gear can have in throwing them off. Diving task loads us to the point that trying something new that 'looks like it'd be simple' is often a problem. I had fun like that in a solo class last year!

At the end of the day, it's not about blaming or looking down on anybody or their experience level. We just don't want to see anybody hurt.

Richard.

 

[John C. Ratliff]

Hi all,

Well I have a cautionary tale called How To Get Bent, otherwise known as The Stupidest Day of Diving Ever. This is a long post and if anyone reads it, I would be glad to hear anyone's opinions...

...The next day I get on the boat and we do a multilevel dive down to about 80 feet at max depth, gradually ascending throughout the dive to maybe 40 feet before surfacing. We were diving based on our dive master's computer and he said it would be "to NDL." I was sucking air out of nervousness and surfaced a good 15 minutes at least before everyone else did (they stayed down about an hour). The mooring line was at 40 feet and as I recall I surfaced along the line at probably a good pace, but who knows, maybe I went too fast? That's not even the best part.

I didn't do a safety stop. Why? I just forgot. How can I defend this? I can't. It was just stupidity.

I was scheduled to do three dives that day but after I got up, I felt OK except seasick. I decided to sit out the next dive and went to the hotel, where I immediately laid down on the hotel room bed and slept for an hour straight. Total surface interval was about 2.5, maybe 3 hours. Went back to the boat feeling great. Did the second dive, the same site, multilevel down to about max 70 or 75 feet this time and I was down a bit longer, maybe 50 minutes instead of 45? Again surfaced before everyone else for the same reason (fast air consumption). Again, dubious ascension and no safety stop. Again, indefensible. Afterward I felt great. We went back to the hotel and everything was fine...

pdxgal,

That is an interesting description you gave. I hope you don't mind, but I'm going to use it as a little review of the U.S. Navy Diving Tables (1971, which is what I have with me now). Your first dive was to 80 feet max for 45 minutes, which according to the Table 1-10 would go to the next higher time of 50 minutes. 80 feet for 50 minutes requires a stop at 10 feet for 10 minutes. For this exercise, we'll assume that your multi-level dive, because of the short time at 80 feet, actually put you still within the no-decompression limits, and effectively served as your decompression stop. But you would be in Repetitive Group "K". Your surface interval was 2.5 hours (conservatively). A surface interval of 2:30 would put you in Repetitive Group "F" according to Table 1-12. Now, if you are calculating your next dive, and it is 75 feet (80 feet on the table), your residual nitrogen time is 28 minutes. So before you began your dive, it was as if you had already been at 80 feet for 28 minutes. But you stayed down for 50 minutes. If you add your actual time of 50 minutes to the 38 minutes RNT you had already accumulated, you get a theoretical dive time of 50 + 38 = 88 minutes. According to Table 1-10, you should have then decompressed at 20 feet for 7 minutes, and 10 feet for 31 minutes for a total ascent time (including the actual ascent) of 34:20. Your new Repetitive Group would be "N" and you would need more than 12 hours of surface interval to go back to a "zero" condition.

This is how we used to compute our repetitive dives in the ol' days.

Now, because you were with an instructor with a computer, and doing a "multi-level" dive, you were not accumulating that much nitrogen in your tissues, because the assumption of the Navy Dive Tables is that you are at that depth the entire time. So you were okay.

The problem I have with your post is that there was no comprehension on your part as to how decompression actually works. Without a computer of your own, you really do not know what your actual decompression was. Without a dive watch, depth gauge and the tables to use to compute the dives like I did above, it is exceedingly difficult to know what your status is with regard to decompression. Flying after the dives could have compounded the problem if there had been a problem, but you would have had symptoms almost immediately.

One thing you may want to do is to go to the following link, and download the U.S. Navy Diving Manual for the I-Pad. (My wife has a new I-Pad, but I haven't dared to use it for this purpose yet--hence the use of my very old dive tables for this example.)

http://vintagescuba.proboards.com/index.cgi?board=general&action=display&thread=2893

In any case, you really should become more familiar with the dive tables and the diving computer. In my opinion, unless you do this you should restrict your diving to 33 feet or less while on vacation. That way, you know you won't have a problem. Don't depend upon others (the dive resort personnel, for instance), especially when diving at a remote location without ready access to a decompression chamber.

SeaRat

PS, I conducted a Google search for the current tables, and the tables have changed a bit since 1971. Here's the challenge to all here. First download the current U.S. Navy Diving Manual:

http://www.usu.edu/scuba/navy_manual6.pdf

Then do the same problem as above, using the new worksheets and tables in the current U.S. Navy Diving Manual. This is a good exercise for all divers, not just "vacation divers."

John C. Ratliff, CSP, CIH, MSPH

---------- Post added January 12th, 2013 at 02:36 PM ----------

Hint: the Repetitive Dive Worksheet is found on page 9-24, and the tables are found on pages 9-62 through 9-71 (to 80 feet of salt water).

SeaRat

 

[John C. Ratliff]

Okay, it looks like no one is going to bite on this little problem, so here's the worksheet on PDXgal's repetitive dive, using the U.S. Navy Dive Tables from Chapter 9 of the new U.S. Navy Dive Manual.

Note that this worksheet assumes that all bottom time was at the deepest depth, and that this would become a decompression dive requiring 114 minutes at 20 feet under these assumptions.

This is why it is important to use your own dive computer for these multi-level dives, as these assumptions are not correct for the type of dive that PDXgal did. What apparently happened was a bounce dive to just over 70 feet on each of these dives. The computer would integrate the actual depth with the time spent at those depths, using different tissue saturation rates to ensure a safe dive. But lacking the dive computer, the dive tables can be used if you go by the Navy assumptions.

SeaRat

 

[pdxgal]

i do not know TSandM except through her post on SB but from those I am sure it is concern for you and others with rusty dive skills that prompted her reply.

I'm sure it was too. I think I must've communicated poorly, because I was meaning to take issue with dividing people into "vacation divers" and "non-vacation divers," not with TSandM at all. I don't know how I gave that impression, because I am sure she's great, as I've already said.

---------- Post added January 13th, 2013 at 07:05 PM ----------

This is going way beyond interesting from a diving point of view, but I guess it's worth another round of posts.
M

You're right, this has gone beyond interesting. I regret even making the comment. Somehow, despite everything I've said repeatedly about me being silly and at fault, people seem to think I am denying my copious mistakes and am defensive about being called out about them, because I objected to one term.

---------- Post added January 13th, 2013 at 07:09 PM ----------

Two red flags to me about the dive company you used were them splitting buddy pairs up, sending you up alone at the end of the dive and that they had no idea about your lack of time between dives. That last one is a big, big red flag. Saba isn't exactly known for timid dives and dive sites, maybe there are some that are easier and safer than others and hopefully those were the ones they took you to.

Lack of time between dives = surface interval? If that's what you mean, they fully knew. I was scheduled to do THREE dives that day, and just sat out the second due to seasickness. So really, they must've felt the surface interval would've been sufficient even had it been less. The buddy thing: Yeah. I thought that was weird too.

---------- Post added January 13th, 2013 at 07:11 PM ----------

Interesting first dive (depth) after an admitted 10 year absence..... can you honestly say you were prepared?

Of course not, the whole point of this post was to illustrate in how many ways I was woefully UN-prepared.

---------- Post added January 13th, 2013 at 07:11 PM ----------

interesting story, I seriously wonder why the dive operator did not ask you when you last dived, most places I have traveled to always ask "when was your last dive?"

With my local dive operator, they insist on a refresher if a diver has not dived for 18 months or more

Yes, after the first day, they mentioned that they should've asked, and apologized, saying it was their oversight.

---------- Post added January 13th, 2013 at 07:12 PM ----------

Tom, I suspect we would fret far less about "vacation divers" if they took your approach. It's the people with the long surface intervals who occasion concern, as the original post in this thread illustrates.

There you go, that's all can ask--to say "vacation divers who have not kept their skills sharp," as in my case. Tom shows it is possible to be a vacation diver who is skilled and prepared. He is indeed who I should try to emulate.