Dive Tables: A Guide to Planning Safe Dives

With the prevalence of dive computers, are dive tables still in use?

The Buggles’ song declared, ‘Video Killed the Radio Star. Yet, audio content is more popular than ever. The internet is teeming with podcasts and new broadcasters. However, it seems the same can’t be said for dive tables… right?

But does anyone still use them? I wonder. And, as is often the case when I have questions about diving, I turn to Victor Cordoba, our expert.

Victor is a scuba diving encyclopedia with legs, the Director of HR at Dressel Divers, a Course Director, Sidemount Instructor Trainer, Technical Consultant for AUP Europe and TECNOMAR, and many more things I won’t list here, because it would take as long as it did for Victor to complete his more than 15,000 dives.

Against all odds, his answer is: Yes, they are still used. — And he continues, ‘Although more sophisticated versions are currently used since the use of traditional tables has significantly decreased with the advent of computers. In the field of technical diving, computer programs based on them are now employed, but they allow for customizing diving parameters, in other words, generating a specific table for each dive. Depth and time are taken into account, as well as safety factors or conservatism. Therefore, they are a valuable tool for planning dives with decompression stops.

Using the dive computer’s plan mode for this is much more cumbersome. In addition, technical divers typically print these customized tables to discuss them among the dive team.

They are also used in commercial diving to predict work times and reduce risks. Basically, they provide support for planning, although later, in the water, divers rely on our computers. After all, they perform real-time calculations and are more accurate. However, you are already prepared for what they are going to tell you because you have used dive tables before‘

Oh, really!? BOOM! My mind is blown, and I come to the realization that there are many people, like me, who think of them as relics, and many others, especially new divers, who don’t even know why or how dive tables are used. And that’s the story of how this article came to be.

In this, we’re going to cover:

1. What Are Dive Tables?

Not too long ago, dive tables were taught in the Open Water course. After all, they were the only reliable tools available to ensure safe dives and prevent the dreaded decompression sickness.

Over the years, different types of dive tables have been developed, such as the U.S. Navy tables, PADI (Professional Association of Diving Instructors) tables, and decompression tables from other diving organizations.

We could define dive tables as printed guides that help calculate the maximum time for a dive in relation to depth and the required decompression time. In recreational diving, this value should be zero.

Decompression tables take another factor into account, which is surface intervals. These allows for planning consecutive dives. The diver plans the duration of the next dive based on the time spent on the surface, during which the body eliminates excess nitrogen absorbed underwater, and the depth to which they will descend.

Diving tables for decompression as no-decompression dive tables, are based on mathematical models and the physiology of the human body under pressure. Now, you might be thinking that you already have your computer for this. But it’s not entirely true. Your dive computers are like wizards (some call them electronic devices) that calculate your decompression in real-time based on your depth and dive duration.

In other words, if things get complicated, both tools are useful. First, dive tables, for example, to calculate the necessary tanks, gas mixes, etc., and then the computer to fine-tune the execution.

2. Evolution of Diving Tables

Dive decompression tables have evolved significantly since they were invented in the early 19th century.

The French physiologist Paul Bert was the pioneer in unraveling the mystery behind decompression sickness. He developed the hypothesis that the accumulation of nitrogen in the bloodstream was responsible for the disease, and he hit the mark. A decade later, the Scottish researcher John Scott Haldane entered the scene, creating the first decompression tables at the request of the British Admiralty. He based them on decompression issues that had occurred during the construction of the Brooklyn Bridge, where pressurized structures were used to build the bridge’s foundations below the water level.

It was in the 1930s when the U.S. Navy left its mark on dive tables. Drawing from their own experiences with divers, they refined Haldane’s work to suit their needs. These adjustments paved the way for the standardization of recreational dive tables in 1980, making diving safer and more accessible for all of us, the aquatic adventurers.

Decompression diving tables have continued to evolve over time. We’ve learned that a decompression pressure ratio of 1.5:1 is safer than the previous 2:1 ratio. Tables were also developed that took into account factors such as breathing rate, body capacity, and individual variations that can affect decompression.

3. Types Of Dive Tables

There are different types of dive tables, also known as decompression tables or immersion tables. But based on their use, let’s differentiate between two types.

No-decompression dive tables, used in recreational diving to calculate dive times in relation to depth without the need for decompression stops.

Decompression diving tables, which also predicted the necessary time required during stops at certain depths to eliminate nitrogen from the body before ascending

Depending on the air mix you use, there are also different tables.

Air Dive Tables: These tables are your allies when diving with good compressed air, with a mix of 20% oxygen and 80% nitrogen, another variable to consider.

Nitrox Dive Tables: Now, if you’re looking for an adventure with a different oxygen and nitrogen mix, nitrox dive tables are your companions. They’ll guide you through the depths while ensuring you avoid decompression issues with nitrox blends.

EAN32 or Nitrox I: 32% oxygen and 68% nitrogen. This is the mix you can find at Dressel Divers and enjoy for free.

EAN36 or Nitrox II: 36% oxygen and 64% nitrogen.

EAN40: 40% oxygen and 60% nitrogen. +

Technical Diving Decompression Tables: These are for experienced divers who often have to make extended decompression stops and gas mix changes. These tables are your secret weapon for planning the tanks you need.   Well, currently they also can use a specific dive software.

4. How To Use Dive Tables

Understand the Basics: Before diving deep, it’s crucial to remember two things:

1. Familiarize Yourself with Your Limits: Understand your personal diving limits, such as maximum depth and the maximum safe dive time you can handle.
2. Get Up to Speed with the Jargon: Dive tables have their own language. Remember that dive tables are an important tool for safety in diving, but it’s also essential to receive proper dive training and experience before using them.

In this article, we’ll only go over some of the key terms, but there’s more to plan for successive dives:

Descent Time (DT): The total time from when you leave the surface until you reach the seabed.

Bottom Time (BT): The total time from when you leave the surface until you leave the seabed.

Total Decompression Time (TDT): The time from when you leave the seabed until you return to the surface.

Total Immersion Time (TIT): The time from when you leave the surface until you return after completing your dive.

 Bottom Depth (BD): The deepest point you reach during your dive.

Choose the Right Tables: As we’ve seen, there are dive tables for air, nitrox, and even technical diving. Choose the set of tables that matches your type of diving.

Find Your Dive Depth: Once you’ve decided at what depth you want to explore, it’s time to find that magic number in your dive tables.

Discover Your Maximum Dive Time: Now, with your depth in mind, look up the maximum allowed dive time for that depth in your chosen table.

Don’t Forget Decompression Time: Thinking about going beyond no-decompression limits? Then, you’ll have to account for decompression time. Dive tables are like your dive GPS, providing recommendations for decompression times at different depths and dive durations.

Calculate the total dive time: Add your maximum dive time and any necessary decompression time (if applicable). This gives you your total dive time, ensuring you stay within safe limits.

Dive, but Dive Smartly: With your dive plan in hand, you’re ready for an unforgettable underwater experience. Remember the forecast made by the dive tables and consult your dive computer to follow the plan precisely in terms of elapsed time, depth, and any necessary decompression stops.

In summary, dive tables continue to play an important role in the world of diving, despite the growing popularity of dive computers. Ultimately, the combination of these tools, along with dive computers, ensures an underwater experience that balances excitement and safety, allowing divers to explore the underwater world intelligently and cautiously. Therefore, while dive computers have changed how we plan and conduct dives, dive tables remain an essential part of diving tradition and safety.