Jan 2015

Diving at Altitude

By Mike Waddington

When you think of mountain sports you will probably imagine skiing, snowboarding, hiking, rock climbing and mountain biking. It may not be the first thing you think of but scuba diving is a popular mountain sport. Mountain lakes offer many things that diving in the sea cannot offer. First of all mountain lakes are usually very clean, some even boasting that it is cleaner than tap water and you can drink it at any time. It is common that mountain lakes are the product of melted snow or glaciers, and as the water is rarely disturbed visibility can be far greater than you could ever find in the ocean. For me the biggest advantage of diving in a lake would be the amazing beauty that surrounds you. Imagine coming up from a dive and seeing snow-capped mountains, alpine forests and beautiful blue skies. It is no wonder that more and more divers are heading to new altitudes on their scuba adventures!

An altitude dive is counted as a dive over 300 meters. This is because as you ascend into the mountains (or in an airplane) the surrounding atmospheric pressure drops, and by the time you get to 300 meters the pressure has dropped enough for the dive tables to not be as accurate as they should be. Today all dive computers can have the altitude changed so they will give you accurate decompression information no matter what altitude you intend to dive at. If you are an old school diver who likes to use tables, depth gauges and timers then you can also get altitude dive tables too that will allow you to accurately track your decompression information. Failing to adjust your calculations leads to an increased risk of decompression sickness so it is very important to double check you have changed your dive computer altitude settings before you descend!

As you are probably aware the air gets “thinner” the higher altitudes you ascend to. By thinner we mean there is less Oxygen available and it becomes harder to breathe. In fact the percentages of different gasses that make up air stays the same no matter what altitude you go to, it is the partial pressure dropping as the atmospheric pressure drops. Because of this our body gets less oxygen with each breath which could lead to Hypoxia (insufficient oxygen). You become hypoxic before or after an altitude dive if you overexert yourself, an easy thing to do when moving heavy equipment around, wearing warm exposure suits and walking around a lot. Signs and symptoms of Hypoxia include fatigue, exhaustion, being out of breath, feeling faint and light headedness. Luckily all you need to do to avoid hypoxia is slow down a bit, maybe carry a bit less gear than you normally would and allow a little more time for getting ready. If you feel any of the symptoms of hypoxia then you should stop all activity and rest for a little bit, when you have caught your breath you can resume activity but go a little slower.

A serious concern of diving at altitude is the cold waters and air temperatures that you may be exposed to. Hypothermia is a potentially life threatening condition that occurs when your core body temperature drops too low. It is very important that you are wearing the correct exposure suit for the water temperature and that you have warm enough clothes for the air temperature. If at any point during a dive you feel cold you should immediately end the dive, dry off and seek warmth. Not doing so will make the situation worse and could make the difference between feeling a little chilly and ending up in hospital. Signs and symptoms of hypothermia include shivering, numbness, cyanosis (blueness of the skin, especially fingers, toes and lips), lack of coordination, confusion, unconsciousness and if left untreated, death. Again hypothermia can be easily prevented by wearing the correct garments for the temperatures and seeking warmth if the diver begins to feel cold.

If you have arrived at an altitude dive site from a lower altitude you will need to allow some time before you go diving. This is because your body will have higher nitrogen levels than the surrounding atmosphere, and as you ascended to altitude the gas has expanded slightly in your bloodstream, almost exactly like when you ascend from a dive. There are calculations to work out how much nitrogen is in your blood, but the easiest thing to do is simply complete a 6 hour pre-dive surface interval to allow yourself to off gas.

Diving at altitude is a great way to mix up your diving if you are always diving in the ocean. It will take you to new amazing places that you had never thought of diving in before. A great fresh water altitude dive site is the Green Lake in the Austrian Alps. It is a park that floods every year (around April to May) from glacial melt water allowing divers to see something truly spectacular, diving in crystal clear water swimming around park benches in a flooded meadow. Altitude diving could be in natural lakes, or man-made reservoirs, each offering interesting sights and their own unique collection of aquatic life. If you live near some great altitude dive sites or plan on visiting them you should read up on how to dive at altitude first, maybe take the PADI Altitude Adventure Dive or Specialty diver course to learn all the different techniques and considerations for diving at altitude.

Diving at Altitude was written by Mike

Photo Credit travelvista.net

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Mike Waddington

I first discovered diving in 2008 after going snorkeling on the Great Barrier Reef in Australia. After trying diving at a flooded quarry in England I decided to head out to warmer more interesting waters in Thailand where I ended on the Island of Koh Tao completing my Open Water course. Instantly addicted with money to spend and plenty of time on my hands I decided to continue until I became a Divemaster so I could live what seemed as the perfect life.

After that I headed to the Caribbean to an island called Utila to complete my instructor course, I spent several months out there completing the MSDT internship, teaching students and leading dives. This is also where I discovered my interest in the technical side of diving, taking part in equipment repair courses and learning about blending gasses and running compressors.

With all my new qualifications it was time to head back to where it had all started, Back to Koh Tao where I intended on living the dream. Once I arrived I quickly found a job and started teaching straight away. During my time on Koh Tao I took part in all many technical diving courses, learning how to dive with re-breathers, in caves and even going down to 90m/300ft!


PADI Master Scuba Diver Trainer
PADI/DSAT Tech Deep Instructor
PADI/DSAT Gas Trimix Gas Blender
PADI/DSAT Trimix Diver
TDI Intro to Cave Diver
TDI Advanced Wreck Diver
TDI Inspiration rebreather Decompression Procedures
PADI Professional Videographer
BSAC Compressor Operator
TDI Equipment Service Technician

Dream Dive Locations:

Silfra, Iceland
Cenotes, Mexico
Chuuk Lagoon, Micronesia
Ice Diving in Russia