One of the questions that seems to get perennially asked on SB is what computer should I buy? or New computer advice needed! There are far greater experts on SB than me (hopefully they will chip in with their own views and advice), but I thought it might be useful to try and collate the gist of the responses that tend to come forward every time this question is asked:
First and foremost, it is your choice. And you should make it based upon the considerations of your own diving plans, now and for the future. The question is usually asked by new divers, so think about it: where is my diving likely to go? Am I going to use nitrox soon? Am I just an occasional weekend diver? How much do I want to invest in this (at the expense of other gear)? Sadly for new divers, there is no real gold standard dive computer that everyone uses. You will need to make a choice from a bewildering large array of options.
What are the factors you need to consider? Well, the main ones are:
Computer vs no computer? The first question is do you really need a computer at all? If you are not going to engage in repetitive diving, or particularly deep diving, then provided you can follow the basic table limits, investing in a computer may be unnecessary anyhow. Conversely, at the other end of the scale, some very advanced divers (specifically those who adhere to DIR philosophies) eschew the use of dive computers, preferring to focus on careful dive planning. That being said, there is probably a very large majority of the diving world between those two poles who use and value their dive computers.
So, if you do decide to get a computer:
Wrist mounted, console or HUD? Some people prefer to have the dive computer mounted on their wrist, others prefer it on their console next to their SPG so that all of their information is in one place. However, if the computer is air integrated with a wireless transmitter, one can still have all the relevant information in one place on your wrist. A comparatively recent innovation is HUD, or heads up display, dive computers, which is jargon for inside the mask. Although it makes for a bulky mask (and an expensive one if you lose it), it does mean that even in literally zero visibility and complete entanglement, you can still read your gauges. Everyone has their own preferences, but wrist mounts tend to be more popular with advanced divers, not least because it does not need to be fixed to a single regulator.
Air integrated or not? Many dive computers have air integrate (AI) pressure gauges, so that they can monitor your air and predict your remaining air time based on rate of consumption and depth, as well as your remaining no decompression limit. The advantage of this is that the computer can monitor and warn you as to your maximum dive time, both due to remaining air and remaining NDL. However, others suggest this ingrains bad habits - relying upon your computer rather than learning to check your remaining air regularly.
If the computer is not a console computer (ie. it is either wrist mounted or HUD), then to be air integrated the air pressure must be transmitted by a wireless transmitter. Whilst this is a neat gadget, they do have a reputation for being flaky, and so normally divers will carry a separate conventional SPG as well.
Air or nitrox or even trimix? All dive computers track your no decompression limit on air, but the cheaper ones can only do air. More expensive computers can also calculate your limits for enriched air nitrox. If you are likely to progress into nitrox, you may want to consider this additional investment. This is probably the biggest decision to make, as having a nitrox enabled computer usually involves the first significant step up in retail price.
However, even amongst nitrox computers, there are distinctions between those which require the dive to be calculated entirely for one gas, and computers which permit gas switches used by technical divers to accelerate decompression. Interestingly, it doesnt follow that all technical divers use expensive nitrox gas switching computers - Rhone Man recalls when he was learning technical diving, he was speaking to some very experienced technical divers on the boat, and they each used a pair of cheap air only computers, even though they used highly enriched nitrox to accelerated decompression. They reasoned that the computers were just a backup, they were cheap, and they wanted the safety factor of knowing they would have been safe even if they had been breathing air the whole of their decompression before ascending.
There are also a small handful of computers which can calculate decompression profiles for trimix and other helium mixtures as well, although these are expensive and it must be very rare that a new diver anticipates getting into trimix diving without substantial further expenditure in equipment and training. Even divers who engage in trimix diving debate whether having a trimix computer is actually useful, given the complexity of trimix decompression schedules.
User replaceable battery or factory replaceable battery? On the face of it, having a dive computer where you can change the battery yourself looks like a huge plus. But there are downsides. User replaceable batteries tend not to last as long as factory replaceable batteries, so you find yourself replacing the battery more often, and the battery usually runs out at the least convenient time possible. Also, there is a bigger risk that you might do something wrong when changing your batter, your dive computer will leak and find a new function as either a paperweight or a door stop.
How conservative? Not all computers are rendered equal. Some computers have are more conservative, and allow shorted no decompression dives. Some dive computers penalise you heavily for skipping the safety stop, or ascending too fast. Others are much more relaxed. Some computers allow you to set it to be more conservative or less conservative.
Below is a table which tries to compare how relatively conservative the main brands of computers are:
However, be wary of putting too much stock in this point. The main benefit of computers is not for a single dive, it is for repetitive dives. All computers are more generous than the tables, because tables rely upon just one tissue group to calculate the benefits of a surface interval, whereas computers will track all, and thereby maximise your benefit.
I dive with two computers - a Suunto (very conservative) and a Sherwood (very aggressive). Frequently the Suunto tells me that I am in deco whilst the Sherwood assures me that I can surface at any time. I just treat it like a long safety stop and dont worry unduly.
Price. Dive computers vary enormously in price - new computers can be as cheap as $200 for basic models, to as expensive as $1,500 for very sophisticated computers. Some people advocated that you buy your last computer first - and go for the most expensive model that you ever likely to need. Others (including me) would suggest starting with a cheaper computer, and then upgrading when you need something more sophisticated (prices keep coming down, and quality keeps going up - waiting often has advantages).
New or second hand? Opinions vary hugely about buying second hand computers. One thing is certain - there are some very cheap second hand computers available on eBay, particularly if you are willing to put up with some cosmetic scratches (I bought my Suunto once for about 1/3rd of retail price). However, as lawyers say: caveat emptor - buyer beware.
Functionality / attractiveness. Some dive computers are sufficiently small that you can get away with wearing them as a watch. Sort of. A big chunky watch. Still, some people value that - if you wear your dive computer as a watch, then you will always have it with you if a diving opportunity suddenly arises unexpectedly.
Models. There are many, many different models of dive computers. It is impossible to run any kind of meaningful comparison, but according to the kind people at Wikipedia, this is a list of the most popular models (by market share):
* Suunto (31.6%)
* Oceanic (27.0%)
* Aeris (11.9%)
* Uwatec (6.6%)
* Mares (5.3%)
* Cressi-Sub (3.8%)
* Sherwood (3.5%)
* Scubapro (3.1%)
* Genesis (2.8%)
* Tusa (2.0%)
* Aqua Lung America (1.3%)
* Seaquest (0.8%)
* Zeagle (0.2%)
Good luck!
First and foremost, it is your choice. And you should make it based upon the considerations of your own diving plans, now and for the future. The question is usually asked by new divers, so think about it: where is my diving likely to go? Am I going to use nitrox soon? Am I just an occasional weekend diver? How much do I want to invest in this (at the expense of other gear)? Sadly for new divers, there is no real gold standard dive computer that everyone uses. You will need to make a choice from a bewildering large array of options.
What are the factors you need to consider? Well, the main ones are:
Computer vs no computer? The first question is do you really need a computer at all? If you are not going to engage in repetitive diving, or particularly deep diving, then provided you can follow the basic table limits, investing in a computer may be unnecessary anyhow. Conversely, at the other end of the scale, some very advanced divers (specifically those who adhere to DIR philosophies) eschew the use of dive computers, preferring to focus on careful dive planning. That being said, there is probably a very large majority of the diving world between those two poles who use and value their dive computers.
So, if you do decide to get a computer:
Wrist mounted, console or HUD? Some people prefer to have the dive computer mounted on their wrist, others prefer it on their console next to their SPG so that all of their information is in one place. However, if the computer is air integrated with a wireless transmitter, one can still have all the relevant information in one place on your wrist. A comparatively recent innovation is HUD, or heads up display, dive computers, which is jargon for inside the mask. Although it makes for a bulky mask (and an expensive one if you lose it), it does mean that even in literally zero visibility and complete entanglement, you can still read your gauges. Everyone has their own preferences, but wrist mounts tend to be more popular with advanced divers, not least because it does not need to be fixed to a single regulator.
Air integrated or not? Many dive computers have air integrate (AI) pressure gauges, so that they can monitor your air and predict your remaining air time based on rate of consumption and depth, as well as your remaining no decompression limit. The advantage of this is that the computer can monitor and warn you as to your maximum dive time, both due to remaining air and remaining NDL. However, others suggest this ingrains bad habits - relying upon your computer rather than learning to check your remaining air regularly.
If the computer is not a console computer (ie. it is either wrist mounted or HUD), then to be air integrated the air pressure must be transmitted by a wireless transmitter. Whilst this is a neat gadget, they do have a reputation for being flaky, and so normally divers will carry a separate conventional SPG as well.
Air or nitrox or even trimix? All dive computers track your no decompression limit on air, but the cheaper ones can only do air. More expensive computers can also calculate your limits for enriched air nitrox. If you are likely to progress into nitrox, you may want to consider this additional investment. This is probably the biggest decision to make, as having a nitrox enabled computer usually involves the first significant step up in retail price.
However, even amongst nitrox computers, there are distinctions between those which require the dive to be calculated entirely for one gas, and computers which permit gas switches used by technical divers to accelerate decompression. Interestingly, it doesnt follow that all technical divers use expensive nitrox gas switching computers - Rhone Man recalls when he was learning technical diving, he was speaking to some very experienced technical divers on the boat, and they each used a pair of cheap air only computers, even though they used highly enriched nitrox to accelerated decompression. They reasoned that the computers were just a backup, they were cheap, and they wanted the safety factor of knowing they would have been safe even if they had been breathing air the whole of their decompression before ascending.
There are also a small handful of computers which can calculate decompression profiles for trimix and other helium mixtures as well, although these are expensive and it must be very rare that a new diver anticipates getting into trimix diving without substantial further expenditure in equipment and training. Even divers who engage in trimix diving debate whether having a trimix computer is actually useful, given the complexity of trimix decompression schedules.
User replaceable battery or factory replaceable battery? On the face of it, having a dive computer where you can change the battery yourself looks like a huge plus. But there are downsides. User replaceable batteries tend not to last as long as factory replaceable batteries, so you find yourself replacing the battery more often, and the battery usually runs out at the least convenient time possible. Also, there is a bigger risk that you might do something wrong when changing your batter, your dive computer will leak and find a new function as either a paperweight or a door stop.
How conservative? Not all computers are rendered equal. Some computers have are more conservative, and allow shorted no decompression dives. Some dive computers penalise you heavily for skipping the safety stop, or ascending too fast. Others are much more relaxed. Some computers allow you to set it to be more conservative or less conservative.
Below is a table which tries to compare how relatively conservative the main brands of computers are:
However, be wary of putting too much stock in this point. The main benefit of computers is not for a single dive, it is for repetitive dives. All computers are more generous than the tables, because tables rely upon just one tissue group to calculate the benefits of a surface interval, whereas computers will track all, and thereby maximise your benefit.
I dive with two computers - a Suunto (very conservative) and a Sherwood (very aggressive). Frequently the Suunto tells me that I am in deco whilst the Sherwood assures me that I can surface at any time. I just treat it like a long safety stop and dont worry unduly.
Price. Dive computers vary enormously in price - new computers can be as cheap as $200 for basic models, to as expensive as $1,500 for very sophisticated computers. Some people advocated that you buy your last computer first - and go for the most expensive model that you ever likely to need. Others (including me) would suggest starting with a cheaper computer, and then upgrading when you need something more sophisticated (prices keep coming down, and quality keeps going up - waiting often has advantages).
New or second hand? Opinions vary hugely about buying second hand computers. One thing is certain - there are some very cheap second hand computers available on eBay, particularly if you are willing to put up with some cosmetic scratches (I bought my Suunto once for about 1/3rd of retail price). However, as lawyers say: caveat emptor - buyer beware.
Functionality / attractiveness. Some dive computers are sufficiently small that you can get away with wearing them as a watch. Sort of. A big chunky watch. Still, some people value that - if you wear your dive computer as a watch, then you will always have it with you if a diving opportunity suddenly arises unexpectedly.
Models. There are many, many different models of dive computers. It is impossible to run any kind of meaningful comparison, but according to the kind people at Wikipedia, this is a list of the most popular models (by market share):
* Suunto (31.6%)
* Oceanic (27.0%)
* Aeris (11.9%)
* Uwatec (6.6%)
* Mares (5.3%)
* Cressi-Sub (3.8%)
* Sherwood (3.5%)
* Scubapro (3.1%)
* Genesis (2.8%)
* Tusa (2.0%)
* Aqua Lung America (1.3%)
* Seaquest (0.8%)
* Zeagle (0.2%)
Good luck!
