I've written about how Cozumel hooked me in 2015, and Part 2 covered the actual dives, the island, and what to do while you're there. This one isn't about the reef. It's about the part every trip write-up skips — the ascent, what your body's actually doing on the way up, and what happens once you're back on the boat — and the part that actually keeps you safe.
The Ascent Is Not a Race
Every dive worth doing puts nitrogen into your tissues. The deeper and longer you're down, the more you absorb. Coming up is where you give some of it back — and how fast you do that matters more than almost anything else in the dive.
Rushing to the surface doesn't give your body time to off-gas that nitrogen properly, and it can also let air trapped in your lungs expand faster than it can escape if you're holding your breath on the way up. Neither of those are things you want to find out about the hard way.
That's why you do a safety stop — three minutes at around 15 feet — on basically every dive, even a shallow no-decompression dive where your computer isn't demanding it. It's not a formality. It's the cheapest insurance in diving.
Decompression, In Plain Terms
Recreational diving within no-decompression limits means your computer or tables say you can come straight up (with that safety stop) without mandatory stops along the way. That's most of what you'll do on a trip like Cozumel.
Push past that limit — depth, time, or both — and decompression stops stop being optional. You owe the water time on the way up, at specific depths, before you're allowed to surface. I've done dives where that obligation wasn't a suggestion, it was a number I committed to before I ever left the boat. That's a different kind of diving than reef-hopping at 60 feet, and it deserves its own post — I'll get into the actual mechanics of deco and technical diving in a future one. This post is just the foundation everyone should have before they think about any of that.
Don't Book the Flight Home Too Soon
Cabin pressure on a plane is lower than at sea level, which is effectively the same thing to your body as ascending further — and you're still off-gassing nitrogen for hours after your last dive, not just the few minutes you spend at your safety stop.
General rule of thumb: at least 12 hours after a single no-decompression dive, 18 hours if you did multiple dives over multiple days, and 24 hours or more if any of those dives required decompression stops. Build a buffer day into the trip. Don't schedule your flight for the morning after your last dive — you're just adding risk for the sake of convenience.
What "Off" Feels Like Afterward
If the current was working against you on a dive — like I mentioned from that first Cozumel trip — you'll probably feel it once you're back on the boat. A little unsteady, balance slightly off, like you're mildly drunk. That's usually just the combination of physical exertion and your inner ear readjusting after fighting current and being weightless underwater. It passes with rest, food, and water.
That's the normal version. The version to actually pay attention to is joint pain, unusual fatigue that doesn't match the dive, tingling or numbness, dizziness that doesn't fade, or skin that looks mottled. Those are signs of decompression sickness, and they don't get better if you wait them out. This isn't medical advice — it's don't-be-a-hero advice: get on oxygen and call DAN (Divers Alert Network) if something feels genuinely wrong, not just tired.
A Few Habits Worth Having
- • Hydrate before and after — dehydration makes it harder for your body to off-gas nitrogen efficiently.
- • Know where the oxygen unit and the nearest chamber are before you dive, not after something goes wrong.
- • Check in with your buddy after you surface, not just before you descend.
- • Skip the second or third dive of the day if the first one left you feeling off. The reef isn't going anywhere.
- • Carry DAN insurance if you dive with any regularity. It's cheap, and it's the one thing you hope you never need.
Cozumel is a great place to learn all of this because the diving is forgiving enough to let you build good habits without punishing small mistakes. Take it seriously anyway. The stuff in this post is boring right up until the moment it isn't.
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Sources
1. Divers Alert Network. "Guidelines for Flying After Diving." dan.org. (12/18/24-hour surface interval recommendations before flying)
2. PADI. "History of the Safety Stop." blog.padi.com. (3-minute safety stop at 15 feet as recreational diving standard)
-Dr Scott