Our Curaçao – a complete guide to snorkeling and diving on Curaçao

Diving is not just about feeling and experiencing — it’s also about measuring and calculating. How deep do you go? How much air do you use? How long can you stay? And how fast are you allowed to ascend? Underwater, surprisingly much revolves around numbers. Fortunately, the math is usually simple — but what doesn’t make it any easier — or safer — is that two sets of measurements and two systems are used.

I grew up in Europe and learned to think in the metric system. When I later learned to dive, that felt natural: depth in meters, pressure in bar, tank volume in liters, consumption in liters per minute. But at the same time, I saw feet, psi, ATA, and cubic feet popping up in the course materials — things that seemed quite exotic to me at the time. I began to realize that divers worldwide actually calculate in two different languages.

And that’s exactly where the problem begins, but also the challenge. For American divers, feet, psi, and cubic feet are not strange or cumbersome units, but the familiar language in which they learn to dive. For dive professionals outside the US, it is therefore useful to learn to understand that system as well. At the same time, the question arises whether a single worldwide system for diving would ultimately be safer and more logical.

In what follows, we’ll first look at how both systems are structured, then how they work in the practice of diving, and finally why standardization might be desirable.

 

The Alchemy of the Imperial System

Let’s first briefly look at where these alternative units come from — a concise introduction for non-Americans to feet and inches, ounces and pounds, gallons and other imperial units.

The foot is one of the oldest units of length in existence and fits in the list of the ell, thumb, palm, (double) pace, span, and fathom: units based on parts of the human body. The foot as a unit already existed with the Egyptians and Romans, but varied as much as human feet themselves. Although there were many historical variants, by the 19th and 20th centuries the British foot and the American foot were practically identical in use. Industry, trade, and science had essentially "smoothed this out" and defined it as a large man’s foot. One twelfth of that is an inch (in Dutch: duim). From there, the system grows further:

12 inches = 1 foot
3 feet = 1 yard
5.5 yards = 1 rod
40 rods = 1 furlong
8 furlongs = 1 mile

Compare that to the metric system:

10 mm = 1 cm
100 cm = 1 m
1000 m = 1 km

Where the metric system works neatly in steps of ten, the imperial system has grown historically and is built from less uniform ratios. You see the same with mass:

1 ounce (oz) ≈ 28.35 grams
16 ounces = 1 pound (lb) ≈ 453.6 grams
14 pounds = 1 stone ≈ 6.35 kg
2000 pounds = 1 short ton (US) ≈ 907 kg
2240 pounds = 1 long ton (UK) ≈ 1016 kg

For weight, there are even several systems alongside each other. The avoirdupois system is used in daily life, while the troy system is used for precious metals — each with their own definitions of ounce and pound. There was also a separate system for apothecaries, again with different units. Even after standardization in 1959, subtle differences remained between American and British units.

With volume, it quickly becomes complex as well:

1 fluid ounce (fl oz)
16 (US) or 20 (UK) fl oz = 1 pint
2 pints = 1 quart
4 quarts = 1 gallon

On top of that, the same name sometimes refers to different quantities: an ounce can be a unit of mass or of volume (fluid ounce). That these roughly correspond for water is a historical coincidence — and that’s exactly what makes the system less transparent. Nowadays, all these units are defined exactly in relation to the metric system. An inch, for example, is exactly 2.54 cm, a pound exactly 0.45 kg (with many more digits after the decimal), and a US gallon — slightly smaller than a UK gallon — is 3.78 liters (also with many more digits after the decimal).

For those who grew up with it, this system works fine. But for outsiders, it quickly feels like a form of alchemy: a historically grown whole with less direct internal logic. At the same time, for American divers, feet, psi, and cubic feet are not strange or cumbersome units, but the familiar language in which they learned to think about diving. For dive professionals outside the United States, it is therefore not enough to dismiss this system as an outdated medieval system — it is at least as important to understand and be able to translate it. Anyone working with international divers must therefore not only master a language like English, but also a second way of measuring and calculating. Even if you speak English fluently, if you only think in meters and bar, you sometimes miss that connection. A good diving instructor is therefore able to switch smoothly between both systems.

In what follows, we’ll look at the main units in which these differences become visible in the practice of diving.

We’ve all had to learn it: diving. Or maybe you’re just about to start — in which case, an exciting journey awaits you.

Learning to dive means mastering a range of practical skills, but also gaining a basic understanding of theory. In most sports — like skiing, surfing, tennis, or kayaking — you mainly learn by doing. Only in a few activities, such as flying, skydiving, or sailing, does theory play a more prominent role. Diving belongs in that category — perhaps more than any other sport.

In practice, you’ll learn how to clear your regulator and mask, equalize your ears, share air in an out-of-air situation, swim efficiently with fins, and communicate using hand signals. But learning to dive also means understanding what happens when you go underwater: how depth and pressure increase, what that does to the volume and density of the air you breathe, and how your body responds. We call this dive theory.

Dive theory can seem complicated at first. Tables, computers, gas laws, safety rules… But the basics of diving are actually surprisingly simple. Once you understand the key principles, almost everything in diving can be traced back to just a few simple rules. In fact, the essence of dive theory fits on a beer coaster. Literally — take a look.