im not sure if i should by a gauge with the psi/depth/and compass or a computer? i know the computers are more expensive but what difference is it? are the computers more complicated? im only a recreational diver. What do the computers do that the gauges don’t other than like the water temp and displaying it digitally? i dont go deeper than 60ft so which should i buy and why? i dont want to spend more than $300

I’m surprised that your instructor didn’t cover this when you were first certified. Recreational divers don’t often dive "square profiles" where they spend their entire dive at a single depth – instead they usually only spend a few minutes at their maximum depth and spend most of the dive at shallower depths. Since the dive computer is constantly recalculating the allowable remaining bottom time based on the dive’s actual profile, the diver gets credit for not ingassing as much nitrogen during the shallower portions of the dive. The dive tables are built on the assumption that the entire dive is spent at the maximum depth attained during the dive. Therefore, the dive computer will allow more bottom time than the dive tables without any significant increased risk of decompression sickness.

Another advantage of a dive computer is that it incorporates both a depth gauge and a bottom timer into a single instrument. You didn’t mention a bottom timer in your gear gauge configuration, but a timer is also an essential piece of dive equipment that every diver should carry since it is vitally important to know how long you have been underwater. Computer timers often start and stop automatically, so they will record your dive time without any action from you other than turning it on before diving. Some computers are air-integrated, meaning they also incorporate a pressure gauge and some even have a digital compass so all your instruments could conceivably be replaced by a single computer that does everything the others do and more.

Some dive operators require divers that do not have a computer to follow a specific profile, which can be quite limiting in terms of bottom time. Computer users may be allowed more freedom to dive their own profile and remain underwater longer.

Even without an integrated pressure gauge and compass on the computer, I believe you can purchase a very capable computer and pressure gauge console for under $300. You may even be able to buy a compass module for your console and keep the total under $300.

The only disadvantage to a computer is that it is an electronic device, and so is more susceptible to a failure than analog gauges. The most common failure is simply running out of power due to a low battery, and can be avoided by replacing your batteries as recommended by the manufacturer (usually once every year or two, depending upon how much the computer is used).

In my opinion, there is no question that you should strongly consider buying a dive computer instead of a gauge-only configuration. If you do buy a computer, I would recommend spending a few dollars extra and getting one that is nitrox compatible. Even if you only dive air now you might use nitrox in the future and spending a little more for that capability may prevent you from having to buy a second computer later on.

Talk to someone knowledgeable at your local dive shop about it.

A couple of comments to Stew’s answer – there is no study that I have seen that conclusively proves that women are more susceptible to DCS than men. "More experienced" divers trained in the 60s and 70s came to that conclusion based on the higher body fat ratio in women combined with the fact that fat tissue absorbs more nitrogen than muscle. However, studies done in the past 20-30 years have not borne out that relationship so there is no reason at this time to believe that women are more prone to DCS than men EXCEPT for a slightly increased risk during their period.

Nor is there any reason to think that dive tables would be any safer than a dive computer based on gender. The fact that the Navy tables were developed for young, fit males is true, but the modern recreational male diver is typically neither young nor fit so the conclusion that decompression theory works better for any man than it would for any woman does not follow from that statement.