Incident due to battery change on dive computer

[TSandM]

It really worries me that someone would ask how you would know what your max depth was if your computer died. If your computer dies, you have been taught to abort the dive at that point; no matter how you go about doing that, you should not have gone any deeper than the max depth you had reached when that computer died. And you should know what that is, because you have been monitoring the gauge at frequent intervals. Honestly, this is one of the reasons I really prefer wrist units attached to the right wrist -- because you can be watching that computer almost constantly, almost unconsciously, as opposed to a console unit that you might have to pull up to look at.

I empathize with the OP a little bit (but not completely). I don't use the deco calculations on a computer, and haven't for about nine years. When I was first learning the method I do use, I kept my computer running as a computer, because I didn't trust myself yet. Like many people I know who do what I do, I eventually forgot to set a Suunto back to 32%, when it had defaulted to air, and halfway through a dive, the gauge was insisting I was in deco, when I darned well knew better. Of course, it locked me out (and I had a spare which had not been diving). I put the offended gauge away and used the other one, and kept using the method I had learned for the rest of the day.

But I HAD a method. The OP didn't, which was the whole problem. He uses his computer to manage his dives, but when he failed to reset it properly, he ignored it and fell back on . . . nothing more than gut feeling. He didn't have personal tools to substitute for his gauge, and he didn't have ANY tools for the second dive at all.

DCS is rare in recreational divers, but a lot of that is due to the fact that the tables are wildly conservative for most "tourist" dives, and dive computers work pretty reliably, and most people make at least some effort to pay attention to them. And the procedure taught to divers, to abort the dive if the computer fails, is a conservative one.

If you are going to ignore your gauge, you need a valid and reliable method to assess your decompression status. Your buddy's gauge is not that method. Reverting to tables and assuming you were in pressure group X at the end of the first dive, will probably work -- IF you weren't in deco at the end of the first dive. The OP was by his gauge and by tables (and by a number of other assessment tools offered by posters in this thread). Therefore, the recreational tables, even assuming an aggressive first dive, wouldn't be a valid strategy, either.

Blaming the OP's instructor for his behavior 1000 dives later seems to me to be stretching it pretty thin. If I get bent using my current decompression strategy, can you blame it on my OW instructors, who diligently taught me tables, and would never have condoned what I am currently doing?

 

[scubadada]

I dive an Oceanic VT3 primary, almost 5 years, more than 500 dives, absolutely perfect. Just started on battery #3. I dive a Geo2/SPG backup, have never needed it but, I could. This would save me from aborted dive and/or series.

 

[stuartv]

Following rules properly, switching to a new computer keeps you out of the water for the rest of the day.

Fixed it for you. As I keep saying, if not missing a second dive is that important, then not having it cut in half or worse is probably important, too. So, the best answer I can come up with is not "use tables". It is spend $200 or less and carry a backup DC with you.

Also, if you don't know your max depth and dive time on a dive you a) shouldn't be diving and b) could just ask the divemaster/guide/buddy. Then switch to a rental PDC. Either way, that rental isn't going to know your tissue loadings.

A) So, you should constantly scrutinize your DC to ensure that you know your exact max depth? Or you should check it every minute or two (or 5) and then when it dies, assume you never got any deeper than the last time you checked? "Close enough" is good enough for you?

B) You would suggest asking the DM, who might be of the same caliber as the one the OP posted about that dived them both into a deco obligation? AND you would suggest to assume that your max depth was no deeper than the DM's?

My point still remains: Using tables wouldn't have helped the OP to be able to do a second dive that day. Having a backup DC with him on the first dive would have. Similarly, using tables wouldn't do much, if anything, to help a lot of people who have their DC die during a Rec dive, and who want to do a second dive that day. Many Rec dives are multi-level and if the diver has even semi-decent consumption, their first dive is going to leave them with a huge RNT, according to the tables, as compared to what a DC would do.

Oh, and what are some examples of dive destinations you know of that you can't rent a computer (meaning to include the possibility of renting a reg set with a console attached that has a computer in it)? I have only been out with 4 (I think) dive ops, spanning the Caribbean and Mexico, so my anecdotal experience is extremely limited. But, they all would rent a diver a reg set, and all of those rental regs included a console with a computer in it. I talked to at least twice as many other operators before booking with the ones I did and they all offered the same.

---------- Post added April 13th, 2015 at 03:26 PM ----------

It really worries me that someone would ask how you would know what your max depth was if your computer died.

Really? At the beginning of a dive, I probably only check my DC every 5 - 10 minutes, depending on how deep it is. As the dive proceeds, I check it more often. That means that I might check it and see 87 feet, then I might hit 93 feet and come back to 87 feet again in the interval before I check it again. Could easily happen. Especially if I check it when I'm over the deck of a ship, then drop down into a hold for a swim-through, for example. And if I come out of the swim-through and find that my DC has died, do you really think I should plan my next dive based on a max depth of 87 feet? The difference on planning between 87 and 93 is a whole pressure group, right? Should I just do a best guess and assume I only went 1 pressure group deeper than the last thing I saw on my DC?

Or are you saying that even at the beginning of my dive I should be swimming with my depth gauge held in from of my face, checking it every 10 - 20 seconds to ensure that if it dies, I could not have inadvertently had a change in depth that would affect future dive planning?

I am fascinated at the responses in this thread. Usually it seems like SB posters are SO anti-guessing. But, here, it seems we have people proposing to guesstimate on things like max depth and bottom time based on "the last max I saw" or "the BT shown on my buddy's DC". Am I really the "conservative" one here? I'm saying that guesstimates and "my buddy's data" are not good enough. At least, not at all good enough when I can have exact data by spending $200 or less to have a backup DC.

Or I can just be prepared to miss the rest of a day's diving and plan to rent a computer (or reg with computer) for the rest of the trip.

 

[RJP]

Fixed it for you. As I keep saying, if not missing a second dive is that important, then not having it cut in half or worse is probably important, too. So, the best answer I can come up with is not "use tables". It is spend $200 or less and carry a backup DC with you.



A) So, you should constantly scrutinize your DC to ensure that you know your exact max depth? Or you should check it every minute or two (or 5) and then when it dies, assume you never got any deeper than the last time you checked? "Close enough" is good enough for you?

B) You would suggest asking the DM, who might be of the same caliber as the one the OP posted about that dived them both into a deco obligation? AND you would suggest to assume that your max depth was no deeper than the DM's?

My point still remains: Using tables wouldn't have helped the OP to be able to do a second dive that day. Having a backup DC with him on the first dive would have. Similarly, using tables wouldn't do much, if anything, to help a lot of people who have their DC die during a Rec dive, and who want to do a second dive that day. Many Rec dives are multi-level and if the diver has even semi-decent consumption, their first dive is going to leave them with a huge RNT, according to the tables, as compared to what a DC would do.

Oh, and what are some examples of dive destinations you know of that you can't rent a computer (meaning to include the possibility of renting a reg set with a console attached that has a computer in it)? I have only been out with 4 (I think) dive ops, spanning the Caribbean and Mexico, so my anecdotal experience is extremely limited. But, they all would rent a diver a reg set, and all of those rental regs included a console with a computer in it. I talked to at least twice as many other operators before booking with the ones I did and they all offered the same.

---------- Post added April 13th, 2015 at 03:26 PM ----------



Really? At the beginning of a dive, I probably only check my DC every 5 - 10 minutes, depending on how deep it is. As the dive proceeds, I check it more often. That means that I might check it and see 87 feet, then I might hit 93 feet and come back to 87 feet again in the interval before I check it again. Could easily happen. Especially if I check it when I'm over the deck of a ship, then drop down into a hold for a swim-through, for example. And if I come out of the swim-through and find that my DC has died, do you really think I should plan my next dive based on a max depth of 87 feet? The difference on planning between 87 and 93 is a whole pressure group, right? Should I just do a best guess and assume I only went 1 pressure group deeper than the last thing I saw on my DC?

Or are you saying that even at the beginning of my dive I should be swimming with my depth gauge held in from of my face, checking it every 10 - 20 seconds to ensure that if it dies, I could not have inadvertently had a change in depth that would affect future dive planning?

I am fascinated at the responses in this thread. Usually it seems like SB posters are SO anti-guessing. But, here, it seems we have people proposing to guesstimate on things like max depth and bottom time based on "the last max I saw" or "the BT shown on my buddy's DC". Am I really the "conservative" one here? I'm saying that guesstimates and "my buddy's data" are not good enough. At least, not at all good enough when I can have exact data by spending $200 or less to have a backup DC.

Or I can just be prepared to miss the rest of a day's diving and plan to rent a computer (or reg with computer) for the rest of the trip.

I wish I knew as much after nearly 1,000 dives as I thought I knew when I had "0-24 dives."

If you think there's a practical difference between 87ft max depth and 93ft you're simply not paying attention to the reality of decompression models. (Please don't tell us that the difference is important because there's a line on a plastic dive table that says "90ft" on it.)

Yes... having a second computer at all times would be helpful. However lots of people dive with only one - and many dive with NONE - with no problems whatsoever. The larger point here, of course is that having TWO computers that are not understood or simply ignored is no better than having ONE computer that is not understood or simply ignored.

 

[Storker]

Using tables wouldn't have helped the OP to be able to do a second dive that day.

Here's where you're totally, patently, indisputably wrong.

You're a rec diver, so you should never incur a deco obligation that can't be cleared by a nice, slow ascent and a three to five minutes' SS at 5m. Assume worst case, i.e. you assume that when you surface you are in pressure group Z. Two hours' worth of SI puts you in C. A three hour SI puts you in A. Residual pressure group C gives you 55 minutes bottom time at 16m. Residual pressure group A gives you 65 minutes bottom time at 16m or 50 minutes bottom time at 18m. It's not rocket science, it's PADI RDP 101. It works even if you have no idea about your max depth, as long as you've stayed inside the NDL.

A dead computer definitely doesn't mean that your diving is over for the day¹. Sure, you shouldn't go to 30m or hang out for an hour and a half or two underwater, but having to stay within OW depth limits and being content with about an hour bottom time is - in my eyes - a minor annoyance compared to having to call it a day. I've had lots of very nice dives within those limits.

¹ One caveat: It would for me, since I use an AI PDC. If, however, it was the trip of my lifetime, I'd bring a backup SPG or make sure I could rent one.

 

[lowviz]

...//... So, the best answer I can come up with is not "use tables". It is spend $200 or less and carry a backup DC with you. ...//...

OK, that works. The point that you might be missing is that some divers won't mindlessly accept blindly following a DC, or even two. You have no concept of the variables at play. So you are off your guess by a few minutes or feet? Look at the difference in minutes of dive time vs. a minute of stop time at fourty feet. Almost an hour. What is it at 110 feet? What is your gut feeling for this transgression?

You have chosen the easy way out. Fly your DC. No prob, it works for you and you most likely won't suffer for it. But please be sensitive to the fact that there are divers who want more understanding than that. That is why Ratio Deco, Deco on the Fly, and other approximations still exist in the face of wrist bling and mindless self indulgence.

 

[Wookie]

Fixed it for you. As I keep saying, if not missing a second dive is that important, then not having it cut in half or worse is probably important, too. So, the best answer I can come up with is not "use tables". It is spend $200 or less and carry a backup DC with you.



A) So, you should constantly scrutinize your DC to ensure that you know your exact max depth? Or you should check it every minute or two (or 5) and then when it dies, assume you never got any deeper than the last time you checked? "Close enough" is good enough for you?

B) You would suggest asking the DM, who might be of the same caliber as the one the OP posted about that dived them both into a deco obligation? AND you would suggest to assume that your max depth was no deeper than the DM's?

My point still remains: Using tables wouldn't have helped the OP to be able to do a second dive that day. Having a backup DC with him on the first dive would have. Similarly, using tables wouldn't do much, if anything, to help a lot of people who have their DC die during a Rec dive, and who want to do a second dive that day. Many Rec dives are multi-level and if the diver has even semi-decent consumption, their first dive is going to leave them with a huge RNT, according to the tables, as compared to what a DC would do.

Oh, and what are some examples of dive destinations you know of that you can't rent a computer (meaning to include the possibility of renting a reg set with a console attached that has a computer in it)? I have only been out with 4 (I think) dive ops, spanning the Caribbean and Mexico, so my anecdotal experience is extremely limited. But, they all would rent a diver a reg set, and all of those rental regs included a console with a computer in it. I talked to at least twice as many other operators before booking with the ones I did and they all offered the same.

---------- Post added April 13th, 2015 at 03:26 PM ----------



Really? At the beginning of a dive, I probably only check my DC every 5 - 10 minutes, depending on how deep it is. As the dive proceeds, I check it more often. That means that I might check it and see 87 feet, then I might hit 93 feet and come back to 87 feet again in the interval before I check it again. Could easily happen. Especially if I check it when I'm over the deck of a ship, then drop down into a hold for a swim-through, for example. And if I come out of the swim-through and find that my DC has died, do you really think I should plan my next dive based on a max depth of 87 feet? The difference on planning between 87 and 93 is a whole pressure group, right? Should I just do a best guess and assume I only went 1 pressure group deeper than the last thing I saw on my DC?

Or are you saying that even at the beginning of my dive I should be swimming with my depth gauge held in from of my face, checking it every 10 - 20 seconds to ensure that if it dies, I could not have inadvertently had a change in depth that would affect future dive planning?

I am fascinated at the responses in this thread. Usually it seems like SB posters are SO anti-guessing. But, here, it seems we have people proposing to guesstimate on things like max depth and bottom time based on "the last max I saw" or "the BT shown on my buddy's DC". Am I really the "conservative" one here? I'm saying that guesstimates and "my buddy's data" are not good enough. At least, not at all good enough when I can have exact data by spending $200 or less to have a backup DC.

Or I can just be prepared to miss the rest of a day's diving and plan to rent a computer (or reg with computer) for the rest of the trip.

You have it a lot right. Yes, carrying a backup PDC is a sure fire way not to lose any dives. Especially if you can get something like a stinger or a D6 or one that looks suspiciously like a wristwatch. See, I wear my Stinger 24 hours a day, 7 days a week. If I happen to fall off a boat somewhere, I have a dive computer with me.

A) I would hope you rarely take your eyes off of your computer. It's on your wrist, right? Just like Lynne said, right? Your hands are somewhere out in front of you when you're in trim, right? Right where you can glance at it every 30 or so seconds. If you don't, it's time to get in the habit, as you seem to be somewhat serious about diving. Yes, if I want to look at my Stinger, I have to roll the wrist of my rashguard back to see it, but my primary computer is right out there for me, my buddy, my buddy's friend, and the parrot fish to see. Every time I look across it.

B) What the DM might know when you ask him/her is what the max depth of the site is. All diving isn't Cozumel or wherever else you've been on your vacations. Most of the places I dive have a bottom. They know when you got off the boat and got back up, so they might be able to give you a pretty good idea if your computer crapped the bed and you made a normal ascent immediately after discovering it. That might even allow you to get onto tables. I'm pretty liberal when someone comes up with a crapped out computer, I'll give them 5 minutes for descent, 5 minutes for ascent, and if they were in 80 feet of water, after 20 minutes off the boat, they might have 10 minutes of bottom time.

I rent dive computers, but not regulators. All of my rental computers are wrist mount. Console mount are for vacation divers.... I say that a little tongue in cheek, but like all gigs, there is some truth to it.

One last thing. As you're cruising the reeef at xx depth, when you get a little more experience, your ears will tell you when you're going shallow or deeper. About every foot. So even if you don't look at your computer as often as I think you should, you should know what has happened to your depth since the last time you did look at it.

 

[victorzamora]

I wish I knew as much after nearly 1,000 dives as I thought I knew when I had "0-24 dives."

I couldn't have said it better myself.

Stuart: you will learn, through experience, that what I'm saying is right. Maybe not the best, certainly not the only, but it's a good way of doing things.

In Roatan, which is the destination I "priced out"above, renting dive computers is by no means a given. my now-wife and I paid for a roatan trip in college, and had no reserve funds for PRIMARY computers, much less backups. I had my watch and tables.

Also, the official recommendation by recreational agencies and most PDC manufacturers is to not dive for 24 hours on the case of a dive computer failure. In Roatan, that could mean 4 missed dives. In Bonaire, that could be 6! Yes. That, to me, is a big deal. Renting a dive computer does nothing for you during those 24 hours. A table would.

 

[Storker]

If I happen to fall off a boat somewhere, I have a dive computer with me.

I'm sure that comes in pretty handy. Because if you ever happen to fall off a boat somewhere, you'll surely spend almost an hour at 18m/60ft, right?

 

[stuartv]

Here's where you're totally, patently, indisputably wrong.

Oh?

The OP said he went to a max of 93' and had a dive time of 46 minutes. What table are you using that would allow him to get back in the water for his second dive that day?