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Altitude Diving

The ultimate altitude diving guide. Dive in crystal clear mountain lakes and explore freshwater diving!

By 15 Min Read
Alberta Lake

This is my ultimate guide to altitude diving. It includes an introduction to diving at altitude, recommendations on where to dive in mountain lakes, and additional tips and tricks.

Please keep in mind, however, that this guide cannot replace thorough and professional training at a dive school or the certification as an altitude diver!

Why should I go altitude diving?

Driving up to the dive spot through a mountain range, taking in the incredible scenery around, and getting more and more excited for the next dive is what makes altitude diving so special.

More often than not, the panorama above water is already worth the trip. I get to experience this firsthand in the Alps on a regular basis.

Incredibly cold, but crystal clear, each mountain lake opens up a completely different world.

Scuba diver in the Green Lake in Austria
What you can see while altitude diving.

What is altitude diving?

Altitude diving (sometimes called mountain lake diving) refers to scuba dives that are done at altitude instead of sea level. Training agencies like PADI and SSI consider any scuba dive above 300 meters elevation (1,000 feet) as altitude diving, while CMAS or iac use 700 meters (2,300 feet) as the reference. Dives above 3,000 meters (9,000ft) elevation are considered extreme or high altitude dives.

At the same time, different altitudes cannot be treated the same.

Just like in mountain climbing, the higher you go, the more extreme effects become. If you went for a hike on a hill at 500 meters you would surely prepare in a different way than when climbing the Rocky mountains at 3,000 meters.

Therefore, some differentiate between general altitude diving and high altitude diving.

When you use a dive table like the U.S. Navy tables, they will account for that by introducing different groups for each altitude.

The Deco2000 dive table, which is more common throughout Europe, instead uses an entirely different table depending on the elevation.

In my opinion, the choice for either definition is not as relevant as understanding how to plan your dive according to the respective altitude.

The best places for altitude diving in the world

Now that you know the fundamentals, you might wonder “where can I go altitude diving?”.

Here are my personal top destinations for altitude divers:

The Alps

In my opinion, the overall greatest place for altitude diving is in the Alps.

Of course, I am very biased with one of Social Diving’s locations set in Munich, Germany.

However, just like in skiing the Alps have a few advantages over almost all other comparable diving locations.

The biggest one is the sheer number of different dive spots to explore.

The Alps feature hundreds of lakes that can be explored in more than 5 different countries.

Castle Hohenschwangau, Germany next to mountain lake
How about this view while diving? Castle Hohenschwangau in Germany.

No matter where you go, you will find a dive spot close by.

In addition, those dive spots each offer different scenery and unique ecosystems. From crystal clear glacier basins to underwater forests and even wrecks, the Alps have it all.

Not only will you find dive spots, but there is also a very good infrastructure for divers, with shops and filling stations everywhere.

Last but not least, the Alps offer diving opportunities at different altitudes. This is especially useful for beginner altitude divers with little experience.

By starting out at lower altitudes and moving up gradually, the risk of altitude decompression sickness can be reduced.

Some of the best dive spots in the Alps include Walchensee (Germany), Blindsee (Austria), Sameranger See (Austria), Vierwaldstättersee (Switzerland), and Wolfgangsee (Austria).

If you need even more inspiration, check out the best mountain lakes for diving in the Alps!

USA

The US features a large number of different freshwater lakes and altitude diving opportunities.

Unlike the Alps, however, these dive spots are located all across the country and can’t really be seen as one single diving location.

You will find rather low-altitude diving at lakes like Summersville Lake (West Virginia) and medium-altitude diving, for example at Rock Lake (New Mexico).

Yellowstone Park lake
One of the highest altitude diving spots in the USA is Yellowstone lake.

However, you can also make a visit to Yellowstone Park and dive at more than 2,500 meters (7,500 ft) elevation.

Lake Titicaca

Many lists of the best altitude diving spots include Lake Titicaca. However, as of November 2022, and the last update of this article, diving here is not yet available for tourists.

Lake Titicaca in Peru
Lake Titicaca can be visited but not dived in.

While archeologists are allowed to dive in there with special permits, and the governments of Peru and Bolivia have been thinking about opening it to the public, this is not yet the case.

Whenever they do allow it, however, you can be sure that we will travel there to experience it first hand!

Fundamentals of altitude diving

Altitude diving in mountain lakes or quarries offers incredible, unique opportunities to explore the underwater world like never before.

Many freshwater lakes in the mountains feature very different ecosystems in comparison to the sea.

Such places also combine beautiful scenery underwater with breathtaking views above water.

However, diving at altitude can lead to an increased risk of decompression sickness, if the dive is not planned out adequately.

There are three parts to an altitude dive which must be taken into consideration.

  1. Travel to the dive spot.
  2. Conducting the dive & decompression
  3. Leaving the dive site

I will give a short description of the challenges involved in each part so that you can get a better understanding, of why I always suggest taking an Altitude Diver special course before going altitude diving.

By no means is this explanation enough to qualify anyone to go altitude diving without proper training.

Pressure at altitude

The factor that makes diving at an elevation different from sea level is the ambient or surrounding pressure.

As you remember from your Open Water Diver course, the pressure decreases, the higher up you move. You can observe that in the image below.

Pressure chart in scuba diving
The pressure drops by 0.1 bar per 1,000 meters elevation

For every 1,000 meters elevation increase, the pressure drops by approximately 0.1 bar (0.1 atm).

That means at the top of the Zugspitze at 3,000 meters, the highest mountain in Germany, the pressure will be at 0.7 bar.

The water pressure, on the other hand, remains the same as at sea level and increases by 1 bar (1 atm) per 10 meters depth.

Knowing this, we can determine the total pressure at each depth for the elevation we plan to dive at.

Taking our example of the Zugspitze at 3,000 meters, a diver at 20 meters depth would experience a total pressure of 2.7 bar.

2 bar from the water pressure + 0.7 bar ambient or air pressure.

Traveling to the dive spot

Every diver knows there is a no-flight time one must adhere to after going diving.

Most training agencies and dive computer manufacturers advise at least a 24-hour delay between the last dive and taking a flight.

The reason is that the cabin pressure is generally lower (around 0.6 – 0.7 bar) than at the dive spot.

After a number of scuba dives, the nitrogen concentration in our body will be increased. Decreasing the pressure even more than directly at the surface at the dive spot can lead to decompression sickness.

Most people do not live in the mountains. Therefore, they need to travel up to the diving location.

Roads through Alps in Italy
Taking a car up to the dive spot over a place means that the nitrogen load does not rise too abruptly.

This increase in elevation leads to lower nitrogen concentration in our tissues and can be thought of as a pre-decompression state.

Subsequently, every dive at altitude is essentially a repetitive dive as our body is already in the process of releasing excess nitrogen we “brought with us” from the lower initial location.

We call this process “equilibration” because we need to first equalize to the pressure at the dive site before we can do any diving.

Equilibration

The equilibration period depends on the elevation of the dive site, as well as our previous one.

It is recommended to wait at least 12 hours for every 700 meters elevation increase before doing any altitude diving.

At the Social Diving Munich location, we are already at an elevation of 500 meters above sea level. Diving at the Achensee in Austria (~ 920 meters elevation) therefore falls under the 700 meters limit and our equilibration period can be shortened.

If we had started the trip at our Frankfurt location (100 meters above sea level), on the other hand, the elevation increase would have been over 800 meters and we would need to spend the night at the dive site in order to dive there.

Keep in mind that traveling by car is “better” in this case, as the pressure decrease happens slower than if we take a plane.

Therefore, diving expeditions to the Himalayas or other extreme-elevation locations require many days of equilibration before any diving can be conducted.

Some dive tables add penalties to the non-decompression limits for shorter waiting times before the first dive.

Nitrogen concentration

Descending during altitude diving is not any different from sea-level diving.
On the contrary, since the total pressure is less at any depth in comparison to the same depth at sea level, the maximum nitrogen concentration is actually less.

A dive to 30 meters depth in the Gulf of Mexico will lead to a total pressure of 4 bar. The partial pressure of Nitrogen – assuming we dive on air – will be 3.12 bar.

A comparable dive at Lake Tahoe (elevation 1,900 meters) will expose a diver to a maximum pressure of 3.81 bar. 3 bar from the depth + 0.81 bar air pressure.

Lake Tahoe in California
Lake Tahoe in Sierra Nevada, California is a great dive spot for altitude diving.

The partial pressure of Nitrogen, respectively, reaches 2.97 bar. Therefore, the total concentration of Nitrogen will be less in the lake.

If you aren’t sure how I derived the partial pressures in either case, check out my article on the most important scuba diving gas laws.

Decompression procedures

One wouldn’t need a special altitude diver course if the above observation had only positive effects on us as scuba divers.

The complicated part about altitude diving arises during the ascend. I can also only give you a brief overview of the most important aspects of decompression here.

Don’t be afraid of the numbers and calculations in this section. It is only to show what happens and is not meant to be memorized.

Pressure ratio

We know from our beginner course that decompression after diving depends solely on pressure differences.

These are larger in shallower water. Therefore, the further up you ascend the slower you may do so.

While it is true that the total pressures during altitude diving are considerably lower than during sea-level dives, the opposite holds true for pressure differences.

We can use the Law of Boyle-Mariotte, to make this obvious:

Boyle-Mariotte formula
The Law of Boyle-Mariotte.

Pressure multiplied by volume remains constant in an enclosed volume. As you know from your beginner diving course, this can be assumed in the water we dive in.

Some of you might remember it in this form, as well:

Boyle Mariotte formula written out
The Law of Boyle-Mariotte written out.

For simplicity, let’s assume the bubble volume v is at 1 at depth.

This means that both v in the formula vanish and we simply compare the ratio of how much the pressure changes during the dive.

During a 30 meters dive, the total pressure at sea level was 4 bar, while at 3,000 meters elevation it was 3.7 bar.

Dividing 4 bar (at 30 meters) by 1 bar (surface) is equal to 4. This is the ratio of how much the pressure changes during the dive in the sea.

Diving at altitude leads to 3.7 bar (30 meters depth at 3,000 meters elevation) by 0.7 bar (surface) which is 5.3.

We can see, the ratio is almost 30% higher in the mountain lake.

Bubble sizing

Why is this important you ask? It’s simple.

While diving, we are always trying to keep the nitrogen bubble sizes in our tissues to a minimum.

Therefore, the greater the ratio is, the larger the bubbles in our tissues can become if we don’t give them time to be “breathed out”.

Since the bubbles can become much larger during altitude diving, we need to account for this added decompression need.

We can do so by ascending slower or adding decompression stops in between.

Your dive instructor will discuss both approaches with you.

Leaving the dive site

Leaving the dive site is not an issue, as long as you move directly from a high altitude to the valley.

In the Alps and other mountain ranges, however, this is not always possible as you might need to drive over even higher mountains in order to get back home.

If the elevation increase during traveling is greater than 300 meters at any point during the drive, you will have to take a sufficiently long break after diving to lower the risk of getting a DCS.

Fun Fact about Lake Titicaca

By the way, did you know diving at Lake Titicaca in Peru and Bolivia, there is no no-flight time? Since the lake is at almost 4,000 meters elevation, the pressure there is at roughly 0.6 bar.

That’s also the lowest pressure you will experience in an airplane cabin.

Airplane flying over clouds at sunset
There is no no-flight time after diving at lake Titicaca. (But you still have to wait!)

Therefore, you may fly right after diving since no pressure difference can occur.

How to become an altitude diver

The easiest and safest way to learn how to dive in mountain lakes is to take an altitude diving specialty course.

During such a course, you and your instructor will go through all the steps of planning, preparing, and conducting an altitude dive.

As you know, I don’t believe a certification card is necessary to make a diver better or worse. However, in this case, the benefits of professional supervision are immense.

Knowledge of the environment

An instructor knows the environment you will be diving into and can guide you. That by itself will make your first altitude diving adventures much more relaxed.

At the same time, the visibility at freshwater lakes in the mountains can drastically change throughout the year.

This is due to the changing seasons and the number of plants and algae in the water.

When scuba diving in Munich or the Alps, for example, we generally experience a sharp decrease in visibility from Mid May to Mid June, and then again toward the end of October.

Lake Starnberg panorama
Lake Starnberg close to Munich, Germany, with Alps panorama in the background.

An instructor knows this and can guide you safely even when the visibility is not great during your course.

Going diving with a professional dive school also means you abide by any laws and regulations in regard to diving permits in that area etc.

Knowing how to find a good dive school for your training is important here.

Quality training

During a course, you receive quality training and advice from a professional who is experienced in the matter.

Diving at altitude poses a number of challenges in comparison to “regular” diving and learning it the right way from the start is incredibly helpful.

I already mentioned the factor of knowing the environment and navigating underwater above. However, there is more.

Instructors who dive in freshwater all the time value the importance of perfect fin kicks because improper technique can disturb the sediment and create silt-outs.

Scuba diving instructor in the water with student
Taking an altitude diving course is highly recommended before diving in mountain lakes.

If you want to know which scuba fin kicks I consider to be “proper”, check out this scuba fin kicks guide.

Second, quality training with an instructor ensures you get to practice the skills needed to dive at altitude. This includes entry and exit techniques, deploying surface marker buoys (SMBs), navigating in zero-visibility areas, and planning dives.

Especially the last point is very important for altitude diving, and as such, let’s look at it in more detail.

Planning an altitude dive

Planning your altitude diving is a crucial step and cannot be neglected or treated as unnecessary.

Let us be honest. When you go on a diving safari, you follow your guide`s instructions on where to dive, when to go back up and how long you wait between dives.

You learned the fundamentals in your Open Water Diver course and assumed the same circumstances on every dive.

As we saw above, however, pressure and decompression change when diving at altitude. An instructor will show you how to use altitude diving tables, computers, and common sense to adjust your dive plan.

Not every student might feel comfortable with using dive tables and that’s why getting certified for altitude diving is a good idea.

Going altitude diving

To end this ultimate guide to altitude diving, here are a few concluding tips for conducting dives at altitude and in mountain lakes:

Enjoy it!

Of course, having fun is the reason to go diving.

Enjoy the scenery above and underwater and maybe even bring a camera to take some great shots in crystal clear water.

Don’t aim for depth

I know, many divers are almost obsessed with depth. The deeper the dive, the better they think it was.

This is not the case here. Take your time, stay shallow if you can, and only go deeper if your dive plan includes that.

One thing I enjoy a lot about altitude diving and lake diving, in general, is seeing the lights, trees, and mountain tops from underwater.

Therefore, I prefer to stay rather shallow during altitude dives and only go deeper if I really find a reason to – which is rarely the case.

Tech diver in lake using flutter kick
Your first altitude dives should not be very deep.

Use proper fin kicks

Using frog-kicks is the way to go in any freshwater environment, or anywhere else, really.

Mountain lakes feature very delicate wildlife and as such may not be disturbed by stirring up sand from the bottom.

Perfect buoyancy

Just like with the fin kicks, perfect buoyancy helps preserve the environment and the ecosystem at the dive site.

Lake diving is much more unforgiving when it comes to poor trim and buoyancy than the sea.

Take that into consideration before diving and maybe put in a few more practice dives before diving at a difficult spot.

Use a drysuit

Mountain lakes can be very cold. Some of them never get warmer than 4°C throughout the year.

Altitude diving requires appropriate coldwater scuba gear and a drysuit is one of the things I recommend.

If you haven’t used one before, why not combine your altitude diving course with a Drysuit Diver course? This way you will not get cold while exploring.

Drysuit diver in lake
Drysuits are usually required for altitude diving.

Combine diving and other activities

Altitude diving will lead you to destinations that offer great opportunities for outdoor activities beyond what’s underwater.

Why not use the equilibration period before diving for a hiking session up to the mountain top?

Don’t forget that you should not exercise after scuba diving, however, mountain areas like the Alps offer so much that you can spend a week there without running out of things to do.

My favorite examples of this are the two well-known mountain lakes Samerangersee and Fernsteinsee.

Located in Tyrol, Austria not even 500 meters apart from each other, diving in them is only allowed if you spend at least one night at the adjacent hotel.

It isn’t just a hotel though, but a castle hotel that offers incredible rooming, great food, and a spa.

Woman hiking along mountain pass
Why not go for some hiking when you’re already up in the mountains?

Besides two of the most beautiful mountain lakes in the world, the area offers other activities like hiking, climbing, mountain biking, rafting, and even golf.

It is also a favorite destination for motorcyclists.

You can spend a few nights here, explore the surroundings and go diving in the lakes. They even have their own filling station!

As they feature extremely delicate underwater plants, the minimum number of dives needed here is 80 for the Fernsteinsee, or 100 for Samarangersee, respectively.

If you are interested in exploring this beautiful place, we can arrange all the travel for you. Contact us and we are happy to make your next mountain lake adventure a success!

Conclusion

This concludes my guide to altitude diving.

If you want to explore beautiful mountain lakes yourself, take an altitude diver course with us in the Alps!

Have you gone altitude diving before? Share your thoughts, ideas, and questions in the comments and discuss with me.

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Always dive with friends and happy bubbles. 😃

Cheers

Julius

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