The Short Answer: Don’t
Scuba diving with a cold is one of the most reliably bad decisions a recreational diver can make. The congestion that comes with a cold — swollen mucous membranes in the nose, sinuses, and Eustachian tubes — directly interferes with the equalization that diving requires. The consequences range from painful to permanently damaging.
Why Equalization Matters
As you descend, water pressure increases — approximately 1 atmosphere of additional pressure for every 10 meters of depth. This pressure compresses the air spaces in your body: primarily your middle ears and sinuses. If these air spaces cannot equalize — meaning, receive air to match the outside pressure — the pressure differential causes barotrauma: tissue damage caused by the mechanical force of the pressure difference.
In a healthy diver, equalization happens easily: you pinch your nose and gently blow (the Valsalva maneuver), or swallow and move your jaw (the Frenzel technique). Air moves through the Eustachian tubes into the middle ear, equalizing the pressure. It takes a second and involves no discomfort.
What Happens When You’re Congested
Congestion swells the mucous membranes lining the Eustachian tubes, partially or fully blocking them. When you try to equalize with blocked Eustachian tubes, you are pushing against a seal. The pressure differential builds. At some point — if you keep descending — either the eardrum ruptures, or the round or oval window membranes inside the ear tear. Both are medical emergencies. Ruptured eardrums cause severe pain and temporary (sometimes permanent) hearing loss. Inner ear barotrauma causes vertigo, tinnitus, and potentially permanent hearing and balance damage.
What About Decongestants?
Many divers take decongestants to dive through a cold. This is not recommended. The problem is timing: decongestants wear off. If you take a decongestant, dive to 20 meters, and the medication wears off before you surface — your Eustachian tubes may reswift while you still have pressure differential to deal with on ascent. “Reverse block” on ascent is arguably worse than a block on descent because you cannot stop the ascent the way you can stop a descent.
FAQs
How long should I wait to dive after a cold?
Wait until you are fully symptom-free — no congestion, no sinus pressure, no ear fullness. For most colds, this means 7–14 days after symptoms resolve. If you had significant ear or sinus symptoms, consider waiting longer and testing equalization in shallow water first.
Can I snorkel with a cold instead?
Snorkeling at the surface involves essentially no pressure change and is generally safe during a mild cold. Duck-diving below the surface creates the same equalization requirement as scuba diving and carries the same risks.