Diving After Flying: Can You Dive the Day You Land?

Is there a waiting time before diving after a flight?

No. The CDC Yellow Book, the US government's travel medicine reference, says plainly that there are no guidelines for diving after flying. It asks divers to wait long enough to settle in, mentally and physically, so they can focus on the dive. DAN (Divers Alert Network) puts it the same way in its trip-planning guide: flying to a destination near sea level before diving poses virtually no risk.

The reason is pressure. An airliner cabin sits at a lower pressure than the ground, and your tissues slowly settle toward whatever pressure surrounds them. A DAN Alert Diver article by Richard Vann describes this for altitude: after about 12 hours, tissues have equilibrated with the lower nitrogen pressure up there. A flight is the milder, shorter version of the same thing. When you land at sea level the pressure goes back up, so you arrive with no extra nitrogen to get rid of. That is the opposite of the dangerous direction.

The dangerous direction is the flight home, when a diver who still carries nitrogen from recent dives goes up to cabin altitude. We cover those waiting times in flying after diving: how long to wait. This page is about the outbound trip, where the risks come from travel itself.

What a long flight does to your body

Three things happen on a long flight that matter for a diver: the air is dry, there is a little less oxygen, and you sit still for hours.

DAN describes air travel as particularly dehydrating because cabin air is very dry, and DAN Europe suggests about 240 ml of water for each hour in the air. Dehydration is thought to make nitrogen washout less effective, which is why DAN Southern Africa lists it among the reasons not to jump in straight off the plane. DAN's own reference chapter on decompression stress adds a caution: dehydration probably gets more attention than it deserves, and dive profile, temperature and exertion matter more. So drink water, but do not treat a full water bottle as protection against a hard dive.

Cabin pressure also lowers blood oxygen a little. In a chamber study of 502 adults published in the New England Journal of Medicine, conditions matching 2,134-2,438 m (7,000-8,000 ft) lowered oxygen saturation by about 4 percentage points, and reports of discomfort rose after 3-9 hours. A smaller study measured healthy passengers on real flights: saturation fell from 97% before the flight to 92% at cruise. This is well tolerated by healthy people and returns to normal after landing, but it is part of why a 12-hour flight leaves you feeling worse than 12 hours on a sofa.

Jet lag, fatigue and alcohol on the first day

Tiredness is the most common reason to wait. The CDC Yellow Book describes jet lag as poor sleep or daytime sleepiness with reduced daytime function after crossing at least two time zones. The body clock catches up at roughly 1.5 hours per day after flying west and about 1 hour per day after flying east, so a trip from London to Bali or from Toronto to the Philippines takes several days to absorb. On trips of three time zones or fewer, the tiredness is usually travel fatigue and passes quickly.

Alcohol makes both problems worse. The CDC notes that alcohol and caffeine can dehydrate you and that alcohol fragments sleep. In DAN's review of drinking and diving, diving skills were clearly impaired at a blood alcohol concentration of 0.04%, a level a 180 lb (82 kg) man can reach with two 12 oz beers in an hour on an empty stomach. Free drinks on the plane and a welcome drink at the resort add up before a morning dive.

There is a hint in the accident data too. DAN Southern Africa reports that 33 of 88 Caribbean decompression cases reviewed for 1994 (37.5%) happened on the first day of a trip. DAN is careful to say those numbers are far too small to prove that travel caused them, which is why there is no formal rule.

Blocked ears and sinuses after the flight

If your ears still feel full or muffled after landing, do not dive until they clear. Eustachian tube dysfunction, the failure of the middle ear to equalize, is often triggered by colds and allergies, and pressure changes when flying can bring on the symptoms, according to an NHS patient leaflet. It describes the feeling as muffled hearing, fullness, popping or ear pain.

The descent on a dive is a far bigger pressure change than the descent into an airport. The first 10 m (33 ft) of water doubles the pressure, while a cabin changes by about a quarter. An ear that struggled on landing will struggle more underwater. DAN's advice on sinuses is short: do not dive when congested. Its ear specialist adds that if equalizing is hard at the start of a dive, it tends to get harder as the dive goes on, and that you can always abort a descent.

Many travelers use decongestant sprays for the flight. DAN warns that repeated use of short-acting sprays can cause rebound congestion, which raises the risk of a reverse block on the way up. Talk to a doctor before relying on them for diving, and review how to equalize your ears before the first descent of the trip.

Blood clots (DVT) after a long-haul flight

Deep vein thrombosis is a travel risk, not a diving one. DAN's Petar Denoble writes that DVT is not related to diving, but divers travel a lot and so are exposed to it. The CDC Yellow Book gives an absolute risk of about 1 in 4,656 to 1 in 6,000 for flights longer than 4 hours. Risk stays raised for about 4 weeks after travel, with most cases in the first 1-2 weeks, so it covers the whole dive holiday.

The CDC lists these warning signs. In the leg: pain, swelling, warmth or a change in skin color. In the chest (a clot that has reached the lungs): unexplained shortness of breath, chest pain when breathing, coughing blood or fainting. Chest symptoms need emergency care. Do not dive with a suspected clot. DAN advises no diving during the acute phase or while taking blood thinners, and a dive medicine doctor's review before returning.

On the flight, the CDC recommends walking around often, calf exercises and, for people at higher risk, below-knee compression stockings of 15-30 mmHg. It also notes there is no evidence that drinking more water or avoiding alcohol prevents travel clots, even though both help with the other issues on this page.

Arriving from altitude, or flying in to a mountain lake

If you live high up, for example in Denver, Johannesburg or Nairobi, and fly to the coast, your tissues are settled at a lower pressure than sea level. Going down to the coast is a pressure increase, the same safe direction as landing from a flight, and we found no source that treats it as a decompression concern.

The reverse trip needs care. Flying from sea level to dive a lake at altitude means your tissues arrive still holding sea-level nitrogen. Vann explains that tissues take about 12 hours to equilibrate at the new altitude, and a dive made before that should treat the extra nitrogen like residual nitrogen from an earlier dive, with a repetitive group assigned. Our guide on how to plan an altitude dive walks through the table and computer settings.

Planning the first and last dive days of a trip

DAN's advice for the start of a trip is to begin gradually with fewer, shallower and more conservative dives, especially after significant travel. That gives you time to rest, rehydrate, adjust to the climate and time zone, and get used to rented gear. The end of the trip is set by the flight home, and our no-fly time calculator shows when your last dive must end.

Here is one way to lay out a 7-day trip with a 10:00 flight home on day 7. The last dive time uses the 18-hour minimum for multi-day diving, counted back from takeoff.

• Sleep before the first dive, even if the boat leaves early the next morning.
• Skip the welcome drinks the night before the first dive.
• Tell the dive guide if you arrived that day or feel jet lagged. You should never feel pushed into a dive while unwell.

Lost luggage and rental gear on the first dive

If a bag goes missing, you may start the trip on rented equipment. Packing the few items you most want to keep, such as mask, dive computer and certification card, in hand luggage limits how much you have to borrow.

Unfamiliar gear is one more reason DAN gives for keeping the first dives easy. Rental BCs, regulators and wetsuits fit and trim differently, and a thinner or thicker suit changes how much lead you need. Do a careful buddy check, confirm your weighting at the start of the easy first dive, and save the deeper sites for later in the week.