High Altitude Diving: Special Procedures and Planning for Mountain Lakes
As Arizona divers, we are no strangers to the beauty of the high country. While we spend plenty of time at Lake Pleasant, the lure of the mountains often calls us higher. Whether it’s the sapphire waters of Lake Tahoe or the hidden springs of New Mexico, diving at altitude is a completely different animal than diving at sea level.
Technically, any dive made at an elevation greater than 1,000 feet (300 meters) above sea level is considered an altitude dive. Because the atmospheric pressure is lower in the mountains, the nitrogen in our bodies behaves differently, requiring specific adjustments to our dive computers and our safety procedures.
Why Altitude Changes the Rules
When you dive in the ocean, you are starting at 1 atmosphere of pressure. When you dive in a mountain lake, you are starting at significantly less. This affects two major areas:
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Decompression Theory: Because the surface pressure is lower, the “pressure gradient” (the difference between the pressure at depth and the pressure at the surface) is greater. This means nitrogen leaves your tissues more aggressively upon ascent. To compensate, your “no-decompression limits” (NDL) are shorter than they would be at sea level.
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The Ascent After the Dive: One of the most critical rules of altitude diving is planning your travel after the dive. If you dive in a mountain lake and then drive over an even higher mountain pass to get home, you are effectively “flying after diving,” which significantly increases the risk of decompression sickness.
Essential Procedures for the Mountain Diver
To dive safely in the high country, there are a few “Golden Rules” we teach in the SSI Altitude Diving Specialty:
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Calibrate Your Computer: Most modern dive computers have an altitude sensor, but you must ensure yours is set to the correct mode before you enter the water.
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Slow Your Ascents: Because the pressure changes are more dramatic near the surface at altitude, your ascent rate must be even slower than usual.
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Master Your Buoyancy: Freshwater is less dense than saltwater, and atmospheric pressure affects your BCD and lungs differently at height. Perfecting your [Perfect Buoyancy] is key to avoiding an uncontrolled ascent.
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Pre-Dive Acclimatization: It’s often recommended to wait several hours after arriving at a high-altitude destination before making your first dive to allow your body to equilibrate to the lower atmospheric pressure.
Popular Altitude Diving Destinations in the USA
The United States is home to some of the most iconic high-altitude dive sites in the world. If you’re looking to take your fins to the mountains, here are a few must-visit spots:
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Lake Tahoe (California/Nevada): Resting at 6,225 feet, Tahoe offers staggering visibility (often 60–100 feet). Sites like Emerald Bay feature “sunken forests” and historic barges.
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The Blue Hole (Santa Rosa, New Mexico): A desert miracle at 4,600 feet. This bell-shaped artesian spring maintains a constant 62°F ($17^\circ$C) and offers crystal-clear blue water that drops to 80 feet deep.
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Homestead Crater (Utah): Located at 5,500 feet, this is a geothermal spring hidden inside a 55-foot tall limestone dome. The water is a consistent 95°F ($35^\circ$C), making it the only warm-water altitude dive in the continental US!
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Clear Lake (Oregon): At 3,000 feet, this lake features a perfectly preserved underwater forest. The trees died 3,000 years ago but remain standing upright in the frigid, pristine water.
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Yellowstone National Park (Wyoming): For the truly adventurous, Yellowstone Lake (7,732 feet) offers the chance to see underwater geothermal vents and unique rock formations.
Take the Next Step with 72 Aquatics
High altitude diving is a rewarding challenge that opens up a whole new map of exploration. However, it is not a “self-teach” skill. The physics of altitude are unforgiving if ignored.
Our SSI Altitude Diving Specialty will teach you how to use altitude tables (if your computer fails), how to adjust your surface intervals, and how to plan your travel home through the Arizona mountains safely.
Ready to reach new heights? Stop by 72 Aquatics in Tucson to chat with our instructors about our next altitude training session or to get your gear serviced for your next mountain expedition.
