Do I really need a computer?

[Kemo Racer]

I've been diving for two years now. I have around 40 dives so far and am a certified rescue diver. I really have no equiptment besides mask and fins but am planning to buy a sp nighthawk and sp mk25/s600. I've talk to several people and they told me that the two most inportant things i need are a reg and computer. I usualy dive in water around 60 degress and only go to depths around 100 ft. I was considering buying a wisdom since my friend owns a store that specilizes in sherwood and good give me an amazing price. The thing is that I don't know if I should get a computer now or wait a couple months. I am planning to go to the galapagos islands for a few days in agust. I just don't know that much about computers and i guess I want to buy a good one that I want have to replace in a couple years yet one I can afford. Thanks and sorry for the long post.

 

[Walter]

No. You don't need a computer. A computer is certainly nice to have, but far from necessary.

 

[ElectricZombie]

No, you do not need a computer. A watch or bottom timer and a set of tables are perfectly fine.

In many ways, I wish I had never bought myself a computer...especially so early on in my diving career.

 

[BILLB]

Dive tables still do a grand job of planning a dive. However, for the RECREATIONAL diver, a well designed computer offers advantages for multi-level diving. It also offers the ability to deviate from your initial dive plan. I know this is almost heresey (Plan your dive, dive your plan) but for most RECREATIONAL dives, you really do not known exactly how to dive an unfamiliar place, wreck or reef until you go down. A computer gives you the ability to safely modify your dive profile during a dive. A computer should NEVER be used to dive beyound your training!

Computers can fail. So can just about anything else you take underwater. If you do purchase a computer and are planning on using it on a multi-day dive excursion, a back up plan should be used. You can continue to chart your dives as a back up using tables. Or, have a back up computer (which must be used on every dive with the primary computer).

If no back up plan is used and your computer fails, a 24 hour no dive interval should be taken before starting diving again on tables or another computer.

No two computers are the same. Read and re-read your computer instructions until you know everything about your computer. Nitrox is the recreational gas of choice for many RECREATIONAL divers. Consider having this function included as part of a computer purchase.

 

[leadweight]

I won't dive without a computer.

Take a typical warm water wall dive. Descend to 65 feet, cruise for 20 minutes and then come up slowly to the shallows at anywhere from 20 to 30 feet for the rest of the dive, which may go over an hour. Surface for an hour and do it again. With tables you are supposed to quit after 40 minutes. After an hour surface interval your next dive would be 9 minutes at 65 feet.

There are multilevel on-the-fly in-your-head calculations that some divers advocate using. Personally, I think a computer is more reliable than my brain on nitrogen. Besides, they don't cost that much if you stay away from fancy air integrated models.

Caveat, for technical dives advance planning with tables or a computer program like v-planner is mandatory. The computer becomes a backup. Aditionally, everyone should know how to use tables.

 

[TX65]

For my first 13 years of diving, I never used a computer. 5 years ago, I bought a Cochran Nemisis IIa because I got an unbelieveable deal on it and was going to Cozumel with a group and the dive operator in Cozumel required that everyone use a computer to keep the group together.

I continued to wear a wrist mount depth gauge, my dive watch and an SPG until one day I left the depth gauge and SPG at home. Guess what happened?.. The computer turned off and for safety I aborted the first dive after descending 10 feet and did not do the second dive. It was a "nice" 4 hours on the boat watching bubbles in the dark (night dive).

Needless to say, I just bought two new SPGs and still have my trusty dive watch and wrist depth gauge. While I still have a computer, I will always have my old fashioned method that served without fail. I also carry Nitrox and Air tables with a small grease pencil on every dive to be able to underline the profile on the table I am running for documentation.

Given that on a group dive with 12 people it is possible to have people on air or nitrox using different computers running different algorythems,,,the argument that it keeps everyone together is overdone.

In addition, I see way too many people who get a computer in O/W and only learn the tables to make it through the class. When they take AOW,,,many have to do a refresher to understand the basics to do any table work in AOW.

Does anyone need a computer or should people be required to have one?....NO.

 

[srkdvr]

A computer is a nice thing to have and does take some stress off you. I have been diving since 89 but just started using a computer 3 years ago and it is alot of help, I still log every dive and check things the old way. But it all comes down to what you are confortable with

Rich

By the way I use the Uatec Sport

 

[Charlie99]

If you are doing more or less square profile dives (low profile reefs, wrecks or other dives where most of the dive is near the deepest depth) then the computer isn't going to make much difference.

Computers won't make much difference if your air consumption is so high that your dives end because of air limitations rather than NDL.

If your dives are shallow (40' or 50') and on a single 80 cu ft tank, the computer probably won't make much difference.

Or if you are using nitrox, it probably won't make much difference in allowed bottom time for dives shallower than 60'.

-------

Where a computer will make a difference is when you are diving to 80' or deeper for at least part of the dive. In these cases, the tables will quickly become the limiting factor, particularly if you are doing these dives with a good multilevel profile. In these cases, the computers automatically track the multilevel dive

A good profile for a Cozumel drift dive is a drop to perhaps 80-85' for 15-20 minutes, then up to around 60' for 10 minutes, then over to the shallower side at 40-45' for another 15 or 20 minutes before ascending to the safety stop. Very good profile with nice offgassing. But on a the tables 81' means you go to the 90' column. Total dive time of 45-60 minutes is WAAAAAY beyond the table limit of 25 minutes.

A computer lets you safely dive this profile

Some say that relying upon a computer is dangerous. I say that you should pay attention to your profile and what your computer is showing. There is no better way to learn what are acceptable profiles than going out and diving. Pay attention to your computer and remember what it said on previous similar dives. Large deviations from what you expect should cause you to do some sort of verification --- like comparing with your buddies computer.

A computer is a great tool for tracking nitrogen loading. Like other tools, it needs to be used wisely.

 

[-hh]

Walter once bubbled...
No. You don't need a computer. A computer is certainly nice to have, but far from necessary.

I agree, but disagree.

While its true that you don't really have to have a dive computer to dive safely (and all that), the reason I disagree is because pragmatically, a dive computer is a tool that among other things, can make diving more cost-effective by increasing your bottom time for a fixed cost dive, and that may be the justification to invest in a computer, even though its not technically "needed".

For a general example, say that we get a hour's worth of bottom time on tables on a $60 dive trip. This means that the cost of that bottom time was (60min/$60) = $1/minute. But if a dive computer would have allowed 70 minutes BT, while our fixed costs remain the same, our effective "per minute of BT" cost drops to $0.86/minute (= 70min/$60)

Granted, this is oversimplistic: we chose to ignore the cost of the dive computer. But this can be accounted for when we look at more than a single dive.

For example, the mentioned Galapagos trip. It depends on what he's planning on doing, but the typical liveaboard as $3K (after staff tip), plus at least another $1K in airfare, transfers and incidentals, which means that a week is going to run around $4K. The diving schedule will give you around 20 dives in that week, so spending $4K for 20 dives works out to $200/dive.

If we assume each dive is 50 minutes on tables, that works out to $4/minute.

Galapagos dives are sufficiently multilevel to allow a longer bottom time, and we'll add in the computer's cost. Let's assume $250 for a basic computer, and an extra 10 minutes per dive.

As such, the calcuation becomes ($4000+$250)/(20dives*60min/dive) = $3.54/minute.

Since this "cost per minute of bottom time" rate went down, it means that the dive computer investment is cost-effective.

The only real hitch with this analysis is the philisophical question of if bottom time is an appropriate measuring stick for making such comparisons. That's a YMMV.


-hh

PS: if your air consumption is good, this same "cost effectiveness" type of evaluation can be done to determine if its worth getting Nitrox too.

 

[MAGELLAN]

Just my opinion, but I'd definitely vote computer. It's not a bad idea to follow up after your dives and see where tables would have landed you. You'll soon see the advantage of using a computer. The beautiful thing about a computer is it's automatic, and never wrong (at least more accurate than me). It can be easy for you to make mistakes when doing multiple dives at multiple levels. If your feeling unsure, just keep an spg and divewatch with you and do both for a while, till you learn to trust the computer, or maybe you decide you like having the backup info, its not a bad idea, just more luggage.