We’ve all had that feeling — you’re in the middle of an incredible dive, hovering somewhere over an amazing view of the bottom when the feeling hits. “I’ve got to go up,” you know. “It’s time to say goodbye.”

All certified divers know that bottom time is a precious commodity. Almost invariably, that’s where the most interesting sights at your chosen dive spot will be. And yet, seeing those sights means you’re in a constant balancing act between air supply, the elements, and your body.

During certification, you learned about the importance of dive tables in helping you calculate that amount of bottom time available at a given sight. Calculations are essential for maintaining safe levels of nitrogen build up throughout your dive. In practicality, though, very few divers actually bother to bring dive tables along for the ride these days. But, that doesn’t make decompression time any less important. Knowing how long you can or need to remain at what depth is still absolutely critical to any dive. However, modern dive computers will handle most of the business of calculating bottom time and decompression time for you. And, they do so more quickly and more efficiently than old school, human calculations can.

The relatively recent advent of affordable dive computers has changed the face of modern diving immensely. Whereas traditional dive tables require you to do mental math and estimate how much bottom time you have, a dive computer can do the job precisely while also taking into account the fluctuations of your depth in real-time.

Ultimately, the end result is less time spent doing mental gymnastics and more time to see the world around you, and more time to immerse yourself in your dive.

One piece of equipment, countless uses

We get it. You can rent a dive computer along with your tanks, but that doesn’t mean you should. Owning your own piece of kit can not only save on rental fees but also pay dividends once it’s set up specifically for your body and—crucially—contains your dive history.

PADI recommends dive computers with an easy-to-read display that provides several data points. At a minimum, your dive computer should show this information: no stop limits, depth, time, no stop time remaining, ascent rate, emergency decompression rates, previous dive information, and low battery warnings. It should also be compatible with enriched air (nitrox). The latter is a big deal and saves you from the massive amount of hand calculations required when using nitrox.

Some dive computers come with optional features like thermometers, compasses, an integrated dive watch, and an integrated air display. Many also include connectivity capabilities with laptops or desktop computers, allowing you to export dive data to analyze or share on social media. (If you’re into that.)

A basic dive computer can be had for around $200. However, more advanced options are available from a variety of manufacturers. Those range upwards of $1,000, though many divers will likely find a happy medium of dive computer features at a mid-range price point.

Choosing the right dive computer for you

Are you a beginner, intermediate, or advanced diver? The answer could determine how much you need to spend on a dive computer.

Most new recreational divers won’t need to drop $1,000 or more to find a capable dive computer for their needs. In fact, simple and more affordable computers in the $200 to $500 range often benefit beginner divers, who are still learning to take advantage of the device’s functionalities. For a beginner, it’s more important to get comfortable breathing, swimming, and navigating underwater than it is to utilize an advanced graph on an ultra-sophisticated dive computer.

These requirements change dramatically for advanced and technical divers, who may find themselves using trimix—a mix of oxygen, nitrogen, and helium that allows divers to go deeper than nitrox—or other gases like heliox that require increasingly complex calculations and readouts. If you’re a technical diver reading this article, you’ve likely had your share of entry-level dive computers and should be perusing the top of the market to suit your needs. However, the vast majority of divers do not fall into this category.

Form factor can come into play when choosing the right dive computer for you. In general, basic dive computers take the form of a large wristwatch, and they’ll serve most beginner and intermediate divers well. The most advanced units tend to feature larger, rectangular displays, the ability to display graphs and models, and performance that goes beyond the normal limits of entry-level units, and a higher price tag to match.

Whichever device you choose should enable a custom profile specifically for your body and your dives. Your dive computer should be easy to operate with thick gloves on and should feature a high contrast display that allows you to easily view it underwater. Otherwise, what’s the point?

Less is more, but not when it comes to safety

Let’s face it, in nature, sometimes less is more. Less technology can equal a greater experience. Less time on your cell phone means more time looking up at the world around you and not down at your screen. Less WiFi means more time to connect with dive buddies and people you meet on your trip. But there’s nothing more important than safety when you’re underwater.

Obviously, air supply comes in first on that list; but a close second place is avoiding decompression sickness. The consequences of miscalculating your decompression time can be severe. Extreme cases of decompression sickness can result in circulatory shock or even paralysis. Even mild cases can force hospital visits and prevent travelers from flying home without a significant waiting period.

Dive computers help you eliminate those risks. They take the guesswork out of the equation by tracking your dive’s progress in real-time. The end result is a safer, and usually longer dive.

While it’s still important to know how to perform your own dive calculations, a dive computer can greatly enhance both the safety and enjoyment of your next dive. After all, when one of the best tools for knowing how quickly you can safely ascend can be tethered to your wrist and automatically calculate that time for you, bringing this piece of technology with you becomes a no-brainer.