What if...? Computer Issues

[Cave Diver]

Ok, time to throw another wrench into the scenario.

You've recently finished your AOW class and for the first dive of the day you're doing a shore dive and exploring the outside of a wreck sitting on a hard bottom. It's a multi-level dive where you and your buddy went to the sand and worked your way up around the wreck as you explored it. You've been keeping a close eye on your computer and consistently checking it every 5 minutes. Neither of you has a backup computer, but you both have tables back on shore with your log books. You are using a wrist mounted computer. Your buddy is using an air integrated computer and he is also wearing a watch that records depth, time and temperature. You are just wearing a standard dive watch. The last time you looked at your computer you had 7 minutes of NDL time left. When you look next, your computer is blank and doesn't respond. You glance at your buddies watch and see the following information:

Spoiler

Question 1: Describe your next courses of action, until you're safely back on shore. Please be as detailed as possible in your response.

Signal your buddy that you have a problem and thumb the dive. You can either let your buddy monitor your ascent rate, or you can ascend no faster than your smallest bubble. You can either use your time at your safety stop to head towards shore, or finish your stop, surface then head in.

Question 2: Based on the information and the circumstances given, can you still make a second dive on the wreck? If no, why not? If yes, explain your dive plan.

Yes. As long as you understand certain limitations! This scenario is informational only and not intended to replace proper safety procedures or good dive planning. The first point to consider is that before your computer failed, you still had NDL time remaining. So you were still within the table limits. However, since tables calculate square profiles and computers do multi-level profiles you have to assume a worst case scenario. Using PADI tables, this means you come out of the water as a Z pressure group. After a 3 hour SI, you're back into the A pressure group and you can plan a second dive based on your repetitive dive group information. Since your buddy has a watch that tracks depth and time, you can swap watches with them so you have a way to monitor that while you dive tables for the second dive.

Obviously the safest course of action is to just skip the second dive, but this exercise is designed to make you think about alternatives. Please do not attempt such a dive without the proper understanding of your tables.

Question 3: Explain what difference, if any, your response to question 2 would be if your buddies dive computer failed instead of yours.

Since your buddy has an Air Integrated computer, not only have they lost their dive information, but their pressure gauge as well. With no way to monitor gas supply it wouldn't be prudent to attempt a second dive.

 

[Cave Diver]

Y'all are forgetting about something...
In addition to the issue of having the same profile on the dive in question, the act of sharing one computer between two divers presumes that the nitrogen loading prior to the start of the dive is the same for both divers. If you've been diving with the same buddy for this particular dive trip and you always dive together on every dive, then that may be more or less true. If you pick up an insta-buddy who's on dive #1 of his dive trip and you've been doing a lot of diving in the last few days (and in particular in the last few hours), then sharing his computer would likely increase your chance of DCS risk.

Correct. I answered based on her response about diving with her buddy. Going off that, I made the assumption that they would share the same dives. If that is not the case, there is definitely an increased risk.

 

[Cave Diver]

What person would want to limit themselves to the dive table square profile when they have a computer?

You might be surprised. A lot more people than you think may be willing to dive a square profile to help a newbie out. I've done quite a few dives below my level to accommodate less experienced divers.

So let's say I rent a computer...how would I be able to take the time to learn all that you need to know about the computer? So, while it would be good to do that, is it really going to be okay?

Most of the rental computers are likely to be lower end models without a bunch of bells and whistles. They might not even do nitrox, so there isn't much to learn that a quick tutorial from the dive op won't cover.

 

[Cave Diver]

Very good point...but I don't want to lose my travel uppy:

What price range is a cheap computer? At least $300, right?

Leisure Pro is showing several air computers under $200 and even one under $150. For less than $300 you can get Nitrox as well.

Computers | Dive Computers at LeisurePro.com

You may also check with your LDS and see what they can do for you. If you have a good relationship they might come close to the online prices and maybe even allow you to do a lay away program.

 

[SeekerOfJustice]

.
First, I must admit that I have been drinking heavily tonight! So, my answers may be off!
Computer Issues
* What would you do if your computer stopped working during a dive?
I will state for good measure that I would thumb the dive. However, in reality my decision here would vary depending on other circumstances. If I was using an air integrated computer I would certainly thumb it. If not, and I was with my close buddy I might stay on the conservative end of his equipment and make an early ascent with Safety stop. Just depends. I dove many times even before I could do math. I could tell time though and read a gauge.
* What would you do if you exceeded your NDLs (table or computer)?
Immediately cease and desist and lay off for 48 hours.
* What would you do if your buddies computer went into deco but yours still showed NDL time remaining?
Happened just last night. Go with the more conservative of the two.
* What would you do if you were gearing up on the boat and realized you forgot your computer and no one had an extra?

Depends. If I'm diving alongside Ed Robinson himself in Maui. I'm not needing that computer much. However, if I am on my own it might be a different story.

 

[Jewls]

I am sure that cleared everything right up for you.

The key is to read Erik Baker, not me.
And definitely don't try to read Bruce Wienke until you've gotten a very good understanding of multcompartment dissolved gas (aka neo-Haldanian, aka Buhlmann) models.

Nope not clear yet, but I think I’ll give the reference materials a read….can’t guaranty I’ll be able to figure out the math equations tho