You surfaced feeling fine. You climbed the ladder, pulled your hood back, and thought about the second dive.
Then twenty minutes went by, and now your hands won't work the clips on your BCD. Your teeth are going. Somebody offers you a towel and you take it, and it does nothing, because a towel has never once stopped wind.
This is the part of diving nobody photographs, it is also the part that decides whether you get a second dive or drive home early. Most divers get it completely wrong, because the thing making you cold is not the thing you think it is.
But be warned: understanding this will ruin the excuse you have been using for years. Once you know why the parking lot beats you, "I was just tired" stops working.
Why do you get colder after the dive than during it?
It has a name...Afterdrop.
During a cold dive, your body pulls blood in from your extremities to protect your core. Your arms and legs get less circulation, and the blood sitting out there gets cold. That is the deal your body makes, and it works fine while you are down.
Then you surface. You start moving, you start warming up, and that cold blood in your limbs finally circulates back to your core. It arrives cold and your core temperature keeps falling for roughly 20 to 40 minutes after you are out of the water.
Divers Alert Network research notes that cold impairs cognitive function, manual dexterity, and judgment. Which is exactly why the dive industry treats rewarming as part of dive planning rather than a comfort question. Cold fingers do not just feel bad. They fumble.
Now add wind. Airflow across a wet wetsuit turns your suit into an evaporative cooler, pulling heat away faster than still air ever could. You are not cold because the water was cold- you are cold because you are wet and the wind found you.
The 7 things that make it worse
1. The towel
A towel absorbs water and stops nothing. It gets soaked in the first minute, then sits on you as a cold wet layer while the wind blows straight through it.
It is the most common piece of post-dive gear in the world and the least effective. We all did it for years.
2. The car heater
This one feels so right that people refuse to believe it.
Blasting hot air at your skin draws blood toward the surface, which can actually slow your core rewarming and deepen the afterdrop. You feel warmer. Your core is not doing better.
Gradual, passive rewarming is what actually works. Get the wet suit covered or off, block the wind, add insulation, and let your body do it at its own pace. Warm drinks help. A hot shower straight out of cold water has the same problem as the heater.
3. Staying in the wetsuit "just for the surface interval"
The suit that kept you warm at depth is the thing chilling you on deck. Wet neoprene plus wind is the worst combination available.
Either get out of it or cover it with something windproof. Standing around in a dripping suit because you cannot face the wrestling match is how the second dive gets cancelled.
4. Assuming a drysuit protects you topside
It does not, not fully. A drysuit keeps water out, but you still lose heat at the hood, the neck, and the wrists. Your undergarments pick up moisture between dives. Wind across the suit surface still costs you core temperature.
Plenty of drysuit divers are colder on the boat than the wetsuit divers who covered up properly.
5. Waiting until you are cold to do something about it
By the time you notice you are shivering, your core has already been dropping for fifteen minutes. Afterdrop does not announce itself early.
The divers who stay out all day are the ones who cover up in the first two minutes, before they feel anything.
6. A regular jacket
Better than a towel, but it fails on three counts. It is not waterproof, so a wet suit soaks it from the inside. It is not cut to fit over 7mm of neoprene, so it will not close. And it is too short, so the moment you bend to strip your suit, you are exposed.
7. Nowhere private to change
The one nobody wants to admit. You are standing in a parking lot, cold, doing the towel dance, hoping nobody walks past. So you do not change, and you stay wet, and you get colder.
The gear problem and the dignity problem are the same problem.
What actually works
Three things, in order.
Block the wind first. Before anything else. Wind is what is stealing your heat, so stopping it is the highest-value move you can make in the first thirty seconds.
Cover or remove the wet suit. Evaporation off wet neoprene is the second thief. A waterproof layer over the top stops it even if you cannot get the suit off yet.
Let your body rewarm gradually. Insulation that still works when it is damp, out of the wind, no blasting heat. Warm drink if you have one.
That is the whole formula. It is not complicated. It is just that almost nothing sold as post-dive gear does all three.
Where the WaterParka came into it
We started designing for this in 2001, and went through seven versions before we sold a single one in 2007. Not because we are perfectionists, but because the first six did not solve all three problems at once.
The Original WaterParka is waterproof outside so a dripping wetsuit does not soak through. It blocks wind completely, with a PTFE membrane rated at 15 CFM, so it breathes instead of turning you clammy. The bonded fleece still holds heat when it is wet, which means you can throw it on over a soaked suit and start rewarming immediately rather than drying off first.
And it has hidden reach-through pockets and an extra-long back hem, so you can peel the suit off underneath it. The parking lot problem, solved without a towel.
It is cut oversized on purpose. For a 3 to 7mm wetsuit, take your normal shirt size. For a drysuit with undergarments, size up one.
Respect the interval. Come prepared. The cold does not care how strong your stroke is or how many dives you have logged. Afterdrop is physics, and physics does not negotiate. The divers who get the second dive are not tougher. They just covered up faster.
Stay sharp. Stay warm. Stay out there.
More questions about staying warm between dives? Read the full dive parka FAQ.
Nothing here is medical advice. If you or a buddy show signs of significant cold stress, stop diving and get medical help. For research on thermal stress in diving, start with Divers Alert Network.