Scuba Diving at Altitude: The Challengers of Altitude Diving

Let me tell you how my friend Ana discovered scuba diving at altitude. Ana has always been an ocean lover, but in a Zen, laid-back kind of way. Her real thrill comes from jumping into the water, feeling the adrenaline, and surfacing with a smile that lasts for days, always ready for her next challenge.

Armed with her Open Water certification, she had already explored half the world, and with her Advanced Diver cert, the other half too. The Caribbean, Asia, vibrant reefs straight out of a dream—she’d seen it all, done it all. Or so she thought.

One afternoon, during an endless scroll through social media, she stumbled upon a story about scuba diving at altitude. “Diving high up in the mountains? Now, this is something new!” she thought.

For some reason, the idea of diving thousands of feet above sea level, surrounded by towering peaks, seemed perfect to her. Maybe it was the challenge. Maybe it was her love for sharing adventurous stories, or the chance to flex on social media and say, “Sure, I dive in the ocean, but I also dive in lakes at over 6,000 feet/2,000 m high. Don’t you?”

At the end of the day, though, what she really craves is new experiences, learning, and feeling alive. For her, life is about living it to the fullest. After all, if she had already dived with sharks in open water, how hard could diving in a lake atop a mountain be?

Well, it turns out there’s more to it than she thought. She knows little about altitude dive tables, high altitude dive computers, or the PADI Altitude Diver certification. But don’t worry—you will, because I’m about to break it all down for you.

1. What is Scuba Diving at Altitude?

The first thing Ana discovered when she dove into the world of scuba diving at altitude was that this wasn’t just a simple underwater adventure. Things are different here when it comes to atmospheric pressure and the partial pressure of oxygen.

Scuba diving at altitude, also known as mountain diving, isn’t just about changing the scenery (goodbye beaches, hello mountains); the rules of the game are entirely different. Diving in lakes above 984 feet (300 meters) above sea level (which is the threshold for altitude diving) is not the same as diving in the ocean. And boy, did Ana notice.

2. What changes diving at altitude compared to sea-level diving?

Partial Pressure of Oxygen

At these altitudes, the partial pressure of oxygen is lower. After all, why do professional mountain climbers carry oxygen systems? The reduced oxygen pressure can lead to hypoxia symptoms, making acclimatization essential.

To avoid unpleasant surprises while scuba diving at altitude, it’s crucial to give your body time to adjust to the height before diving. A general recommendation is to wait at least 12 hours at the location before diving, but this acclimatization period depends on several factors like local conditions and individual factors. In fact, when diving above 8,200 feet (2,500 meters), a minimum acclimatization period of up to 48 hours is suggested.

And we haven’t even gotten into the water yet.

Atmospheric Pressure

You might think that because atmospheric pressure is lower at altitude, divers at altitude absorb nitrogen more slowly, reducing the risk of decompression sickness, and allowing for more dive time. WRONG.

Did you know that? Ana didn’t either—she had to find out the hard way. She quickly realized that planning a dive at altitude is even more important. Decompression (which occurs in every dive) needs to be carefully managed because, at altitude, it actually takes longer. Plus, sea-level tables and procedures don’t directly apply to high-altitude diving. Corrections are necessary.

The thing is, in high-altitude diving hydrostatic pressure (water pressure) doesn’t differ much from sea level, but the atmospheric pressure is lower, as we mentioned before.

So, all the intermediate pressures change as the diver ascends. The higher you go, the more they differ. Surprised? Well, you should be spending a little more time in the water.

For example, if you’re diving in a lake at 9,842 feet (3,000 meters) and you plan to reach a depth of 92 feet (28 meters), it’s equivalent to being at 130 feet (40 meters) in the ocean.

And now, your mind might be blown: to avoid having to make decompression stops like technical divers do, when scuba diving at altitude, you have to spend less time at the bottom. Amazing, right?

So, when you’re diving in mountain lakes, you need to be more alert than ever. Altitude divers must adjust their techniques: more conservative dives, more precise calculations using altitude dive tables, and something Ana had never considered before—acclimatizing to altitude. To avoid surprises underwater, allowing your body to adjust to the height before diving is essential.

3. Considerations and Preparations for Scuba Diving at Altitude

Ana realized that if she wasn’t careful, she could end up facing decompression issues, which was definitely not part of her bucket list for her high-altitude diving adventure.

3.1. Training to Become an Altitude Diver

In commercial and scientific diving training, the effects of altitude on decompression are taught, as well as how to calculate necessary corrections. However, this isn’t always the case in recreational diving. For example, Ana didn’t know—or couldn’t remember—how to make these calculations.
So, she decided that the first step was to get trained and signed up for an SDI Altitude Diver course. There are other options as well, like PADI or NAUI.
Her instructor was fantastic and explained that the key to altitude diving is knowing your gear and how it works.

3.2. Altitude Diving Gear

Dive Computer
With her typical energy, Ana already had her dive computer, but soon discovered that not all computers are suitable for high-altitude diving. Standard dive computers are designed to work at sea level, but when you ascend to higher elevations, the pressure changes, and the computer must be able to adjust its decompression algorithm. So, the first thing she did was check if her equipment could switch to altitude diving mode.

Modern dive computers handle this by automatically detecting altitude changes or allowing the user to manually adjust the settings. If Ana’s gear lacked this option, she would need to use the good old altitude-specific decompression tables. These tables are crucial to ensuring the body has enough time to safely release accumulated gas as you ascend. Without them, the risk of decompression sickness is much higher.

Depth Gauge
Ana also took the time to research her depth gauge, as not all work the same at altitude. Gauges using Bourdon tubes, diaphragms, or digital sensors may require adjustments to be accurate in these conditions. In the end, she opted for a capillary depth gauge, which experts consider a conservative and reliable method for measuring depth at altitude.

Regulator
Additionally, Ana realized that the regulator she had used in her tropical dives wasn’t necessarily the best for these cold, high-altitude waters. The higher the lake, the lower the temperature, so her regulator needed to be prepared for cold conditions. The last thing she wanted was to run out of air or have a frozen regulator in the middle of her underwater adventure.

Dry Suit or Semi-Dry Suit
Another item Ana needed to acquire was a dry suit. Although they cost a small fortune, she was assured it could last a lifetime with proper care. For warmer locations, a semi-dry wetsuit would suffice, but always with a good pair of gloves and boots—she didn’t want to come out of the water with frozen toes!

Dive Knife
One of the things Ana was most excited about was the idea of seeing the impressive freshwater plant life, like kelp forests. However, she was also warned that she could get tangled in them. So, naturally, she had to upgrade her old dive knife, which was well past its prime.

After a few practice sessions at a local pool, Ana was ready to go out and explore. But not without doing a quick mental checklist first. From her suits and knife to her dive computer (adjusted for altitude), everything needed to be in place.

4. Popular Destinations for Scuba Diving at Altitude

When we talk about scuba diving, most people think of warm tropical destinations, but scuba diving at altitude takes you to another level—literally. Exotic and unexpected locations become accessible to adventurous divers like Ana, who are looking to explore beyond coral reefs and the crystal-clear waters of the Caribbean.

One of the most well-known altitude diving spots in the United States is Lake Tahoe, located on the California-Nevada border at an altitude of 6,200 feet (1900 meters) in the Sierra Nevada. With clean and clear waters, this lake offers a unique experience, although the temperatures can be challenging: in winter, they hover around 40°F/ 5ºC, and in summer, they barely reach 60°F. It’s not your typical warm diving destination, but the water clarity and the sensation of diving in a mountainous environment make it a must-stop for altitude divers.

Another iconic high altitude diving destination in the U.S. is Yellowstone National Park in Wyoming, where divers can explore geothermal hot springs about 7,700 feet (2,133 meters) above sea level. The contrast between the cold environment and the warmth of the hot springs creates a place as spectacular as it is surreal.

Across the Atlantic, Europe offers hidden gems as well. Austria is known for its mountain lakes, perfect for those who enjoy cold-water diving. Additionally, in the Pyrenees between France and Spain, the bravest divers can try ice diving, an experience that truly tests your skills and endurance.

But not everything is cold. If you’re looking for a slightly warmer destination, Lake Atitlan in Guatemala is perfect. Located about 5,100 feet (1,600 meters) above sea level, this lake lies within a volcanic crater in the highlands of Guatemala. Famous for its natural beauty, it offers the chance to scuba dive at altitude surrounded by active volcanoes, making it an exotic destination that promises unique adventures.

For those interested in altitude diving in Asia, the Fuji Five Lakes region in Japan offers a fresh-water altitude diving experience with an impressive view of the iconic Mount Fuji. It’s not just the altitude scuba diving that draws adventurers here, but also the spectacular views of the landscape surrounding these lakes.

What Makes These Destinations Special?

What all these destinations have in common is the mix of natural majesty with the exclusivity of diving where few have gone before. For Ana and other divers like her, the opportunity to explore mountain lakes and volcanic craters elevates the diving at altitude experience to a new level. The feeling of being in remote, isolated places, surrounded by snow-capped mountains or volcanoes, adds a sense of adventure not found in traditional diving destinations.

These sites are not only challenging due to their altitude but also because of environmental conditions such as water temperature and visibility. However, for divers seeking a challenge and an experience that is truly out of the ordinary, scuba diving at altitude offers the opportunity to explore the unexpected.