Noob computer questions

[victorzamora]

I've seen divers who were not using computers OR tables just blindly follow divemasters, and I think that's the worst of all worlds.

This was me for a long time (hundreds of dives). My buoyancy and trim were pretty good (for someone who had never been exposed to truly good divers), and I was VERY comfortable underwater.....but I was totally useless diving alone. I didn't realize many people dove without following a DM, and thought computers were for people trying to show off.

That's one reason that I try to recommend a computer as a first piece of dive gear. It's not needed, but it immediately makes you more independent. If you get a dive computer and learn how to use it, you'll be much better off than I was. I knew how to use tables, but I never really did. Looking back, I'm VERY lucky everything went alright.

 

[boulderjohn]

A computer can be used to plan a square profile dive the same way a table is used. You go to the planning mode and find out the NDL for the planned depth of the dive. If you want to limit yourself to that, then go ahead and limit yourself to that.

I got certified to dive in the late 1990s and took my first trip to Cozumel. I brought my tables with me and trotted them out for the first dive. After the initial laughter of those around me subsided, they explained that if I wanted to do the dives everyone else was doing, I had better get a computer. If I wanted to dive the tables, I had better be prepared to ascend long before everyone else. I bought a computer.

I have done many hundreds of recreational dives all over the world. That time that I brought out my dive tables in Cozumel remains the only time I have seen anyone bring out tables to plan or record a recreational dive (other than in classes). You can argue the superiority of table diving for recreational dives all you want--the simple fact is that people aren't doing it.

 

[doctormike]

The main advantage of computer diving over tables/square profiles is that it gives you "credit" for time spent above the planned bottom depth. For most divers, this is a significant increase in NDLs.

Whether or not a significant increase in NDLs results in a significant increase in dive time depends on whether the diver is gas limited or NDL limited. For lots of occasional and/or new divers, they are gas limited, so they don't get that much of an advantage. However, the small cost of a dive computer (in the context of the overall cost of diving) which eliminates the need for table work is probably worth it, even if it doesn't increase your dive times...

 

[mathauck0814]

I tell everyone the same thing. Buy the cheapest, wrist mounted, nitrox compatible computer with a gauge mode that you can find. You can dive that for the rest of your career. If you find that you start getting into more complex dives, whatever is available now will have been updated and you can look at the state of the art then.

Hollis makes some pretty nice options that fit the bill - the DG-02 is more computer than most divers will ever need - at <$300. Use the rest of the budget to go diving.

As big a fan of Shearwater as I am (and I am a huge fan, I own six), telling a new diver to shell ~$900 on a fully enabled technical diving computer is just foolish. By the time the diver gets around to using anything resembling the full features of that machine, the Petrel will be out of service and a whole host of new toys will be available.

 

[boulderjohn]

The main advantage of computer diving over tables/square profiles is that it gives you "credit" for time spent above the planned bottom depth. For most divers, this is a significant increase in NDLs.

Whether or not a significant increase in NDLs results in a significant increase in dive time depends on whether the diver is gas limited or NDL limited.

It can also depend greatly on the specific dive profile. I once did a dive that I have used in classes as an example of the difference. It was a site in Curacao, and the briefing said there was a sandy patch with garden eels at 100 feet. I like garden eels. I went down to 100 feet for a little less than two minutes to watch them and then ascended to the middle of the reef for a while. I then went to the top of the reef for the remainder of the dive. I ended up doing a dive of well over 60 minutes on an AL 80 tank, and I never got anywhere near NDLs on the computer. If I had been diving tables, I would have been required to ascend when I reached 20 minutes. Now, most multi-level dives are not made to such extremes of depth differences, but that is the essence of multi-level diving as it is done on recreational dives all over the world.

 

[jongles]

I'm happy with my suunto vyper, the plan is to add it to my console as a backup if i ever do upgrade to something more fancy.

 

[doctormike]

As big a fan of Shearwater as I am (and I am a huge fan, I own six), telling a new diver to shell ~$900 on a fully enabled technical diving computer is just foolish. By the time the diver gets around to using anything resembling the full features of that machine, the Petrel will be out of service and a whole host of new toys will be available.

Well, yes, you have a point. But if you are comparing it to a similarly priced "watch" computer, I don't think that the price is necessarily a deal breaker.

I think that it's really nice to have a large, very readable display. I find this especially true as my eyes get older. I don't know another computer with that kind of visual appeal, but then again, I might be missing one. The Xdeep Black might be in that category, but it isn't as big and doesn't have the easily changeable AA battery that the Petrel has. Xdeep is $429 as a bottom timer, then for an extra $200 you can upgrade the software to a nitrox dive computer (and for $200 more, trimix!). For me, the extra $200 for the Petrel (over the Xdeep with nitrox software) was worth it, since Shearwater has amazing tech support, a great track record and lots of dealers all over the world, while Xdeep has taken a long time to get their computers to market.

The Petrel in recreational mode is very user friendly for the average recreational diver, and is a great computer even if you never end up doing a gas switch under water. So it's not that I'm recommending it because it's a fully enabled tech diving computer, I'm recommending it because it's a terrific recreational computer and if you can afford it, it might be something to consider. The difference between the Petrel ($850) and a low end $300 computer is a lot less than the cost of many short dive trips.

 

[guyharrisonphoto]

I concur with the recommendations for a moderately priced computer. My choice of them all would be the Hollis DG-03, a tremendous buy at around $250.00. It runs a well established algorithm (Buhlman Z 16), nitrox, very readable, has a very good gauge/timer mode, really, everything you need or want for quite a while into the future. The $600 you save over a petrel or something similar can buy you at least a dozen dives, which is something far more worthwhile for a newer diver.

It can definitely "grow" with you. It does up to three gasses, so if you ever get advanced recreational training like advanced nitrox/deco procedures (as far as you can go without getting into formal technical), it will work well for that.

If you go tech, it is a great depth/bottom timer for table dives.

You can also add later (or now), as an option (or not), Wireless Gas Integration. This is a great convenience feature and gives you invaluable data on your gas consumption under various conditions, another great benefit for a newer diver seeking to learn and advance his dive training and gas planning. Most criticisms of this feature are by technical divers who do not understand how advanced rec divers use it. That is, for data and convenience, in addition to, but never a replacement for, a traditional SPG which is clipped off in an unobtrusive spot but always available if there is a signal loss from the transmitter (something that has not happened with my computer). I have recently activated this feature on my computer and I must confess I am very glad I did. By the way, I am "old school" trained on tables from the 70s, the traditional spg, and a hogarthian rig, but it is easy to recognize the benefit of these advances and deal with their limitations.

Finally, as for "plan the dive and dive the plan" based on square profile tables, just forget about that. I (old school, remember?) started computer diving three years ago. I am astounded how much better, more enjoyable, and, yes, even safer the computer makes diving. You still should understand tables (I have the NDLs memorized) and basic deco theory, and understand what the computer is doing with its algorithm, but it is just no contest. So, get one and use it!

To echo Boulderjohn. My wife and I were in Curacao at a favorite site. We had steel HP 120s so we were not gas limited. There was Black coral at 130', a sloping wall just covered with corals and tropicals, and a sandy "bowl" full of great macro life at 15'. We swam out and down the wall to 130. When the computer gave us the one minute warning, we began a zig-zag ascent following the sloping wall. All along the way, we watched the computers and moved shallower until the NDL went up to 5 minutes or so, then repeat all the way to shallow bowl which doubled as a huge safety stop as we chased the tiny critters.

In the end, over 70 minutes of dive time and never a deco warning. We ended up "gas limited" in the end as we could have stayed even longer.

This was a classic case of "flying the computer" because we understood what it was calculating and that it was giving us credit for our shallower ascent depths.

Am I going back to "old school"? I don't think so for rec dives.

 

[RandomGuy1]

Thanks for all the great responses. I think I have decided to forget going with a watch sized dive computer and go for a larger wrist mount for visibility. I have good eyes for now, but who know what the future holds. I am leaning towards the Suunto Vyper as one of the local dive shops carries it. I do want one for my own safety so I can watch my own numbers easily vs diving with tables. My basic plan is to dive the tables and use the computer as backup until I get more experience. I like the idea of being able to electronically log my dives and make notes. While the Shearwater is probably a great computer right now, by the time I would move to diving that would even come close to requiring that level of computer, I would likely be ready for a new computer anyway.

 

[doctormike]

I concur with the recommendations for a moderately priced computer. My choice of them all would be the Hollis DG-03, a tremendous buy at around $250.00. It runs a well established algorithm (Buhlman Z 16), nitrox, very readable, has a very good gauge/timer mode, really, everything you need or want for quite a while into the future. The $600 you save over a petrel or something similar can buy you at least a dozen dives, which is something far more worthwhile for a newer diver.

I think that I may have given the impression that I am recommending the Petrel for all new divers. Sorry if it came off that way.

Readable is a relative term - at least for me, there is a big difference between the standard small monochromatic passive matrix LCD display on most entry level dive computers and a large color active matrix LCD display on the Petrel (both in terms of readability and the data available at a glance). Does this mean that everyone should only buy a computer with this type of screen? Of course not. But if you find that this makes a difference to you, then it might be worth the extra money. Just like buying a better fitting and more comfortable dry suit, a better breathing regulator, or any other piece of gear that is available in many different styles, it is sometimes worth spending more to get something that is better for you.

Hey, you can save a lot of money by diving in Florida instead of diving in the Galapagos islands, but you wouldn't say that no one should dive the Galapagos when you can take that money and buy more Florida dives, right? It's rarely a zero sum game like that.