Scuba Diving

The camera is packed, and the tank gauge was a glance on the way to the ladder. About 20% of a dive decides whether it stays a dive, and the other 80% is buoyancy practice plus a longer bottom time. Breathe the whole way up, turn while there is still gas, and come up slowly. A held breath on the ascent is how a lung tears.

Breathe the whole way, including the way up

Scuba puts compressed gas in your lungs. If you hold your breath and ascend, that gas expands. The injury is a torn lung and arterial gas embolism. It can happen from a shallow depth. Training agencies teach one rule ahead of the camera: breathe continuously, and never hold a breath to stretch a photo or a swim to the boat.

Slow breathing can calm you and save gas. "Extend your bottom time" by sipping the tank down is the opposite lesson. Bottom time ends when you still have a reserve, not when the camera is done. Divers Alert Network's notes on fatalities tie rapid ascent and pulmonary barotrauma to air embolism (DAN health and safety guidelines).

In the DAN annual report's 2015 fatality file, a trigger could not be established in 33 of 67 cases, about 49%, mostly because the investigation was thin. Where a trigger was named, an underlying health problem and running low or out of air led the short list (DAN Annual Diving Report, 2017 edition). Do not turn a half-empty file into "80% of deaths are one mistake." Do turn the dive while you can still breathe.

Gas, depth, and a turn you decided in advance

Before you leave the surface, say the turn pressure out loud. Many divers use a reserve that gets them up with gas still in the tank, plus whatever the plan and the agency require. Check the gauge on a schedule, not when you feel starved. If you are low, signal and ascend with your buddy. Do not sprint for the boat on an empty lung.

Ascend slowly. A common training ceiling is no faster than 30 feet (9 meters) per minute, with a safety stop when the plan calls for one. Your computer is the authority on that dive. Chasing it from depth because you are late is how a manageable dive becomes an embolism or a decompression injury. This page will not replace the tables or the computer.

The ignored majority is the next certification card, a bigger camera, and a longer bottom time "because buoyancy feels good." Buoyancy protects the reef and your gas. It does not license a held breath.

Five skills, until they are dull

Practice these in a pool or a shallow site with an instructor, not for the first time on a drift dive: mask clear, regulator recovery, a shared alternate air source, a controlled ascent, and hovering without sculling your hands. One drill this month is enough. Pick the one you last fumbled.

Drill, the turn call: on the next three dives, write the turn pressure on your slate before you splash. When the gauge hits it, you turn, even if the turtle is still ahead.

Open-water panic that is not scuba, including rip currents, is on swimming. A life jacket for a boat ride to the site is on sailing and kayaking. The jacket does not go in the water with you on scuba. The breathing rule does.

Health is a real trigger, not a footnote

The DAN file keeps finding hearts and other medical problems among the triggers that could be named. If you have chest pain, are being treated for a heart or lung condition, or felt unwell before the boat left, sit out. A dive physical is the right place for that question. This article is not that exam.

Illustrative: the diver could hover like a photograph and still held a breath for the last ten feet because the boat ladder was close. The rule they skipped was the one the agencies put first.

8020 move: on the next dive, name the turn pressure before you get in, and breathe out the whole ascent. Leave the camera on the boat until both feel ordinary.

Misreads that stretch the tank

"Buoyancy is 80% of safe diving." Buoyancy is a large part of a calm dive. The lethal rules are continuous breathing, gas left for the ascent, and a slow trip up.

"Slower breathing should extend bottom time." Slower breathing can save gas. The turn pressure still ends the dive. Empty is not a style.

"Half the DAN cases had no trigger, so the rules are guesswork." Missing data is why you do not invent a percent. It is not permission to hold your breath.

Sources

• DAN Annual Diving Report, 2017 edition, 2015 fatalities. A trigger was missing in 33 of 67 cases, about 49%. Named triggers were led by health problems and low or empty gas. Do not pretend the missing half is a clean ratio.
• DAN health and safety guidelines. Rapid ascent and pulmonary barotrauma are tied to air embolism. Breathe continuously. Do not hold a breath on ascent.
• This is not a certification, a decompression procedure, or a reason to dive with a medical problem you have not asked about.