Why Divers Should Care About Surface Intervals
Most divers glance at their dive computer’s no-fly timer, see that it is counting down, and assume they are ready for another dive after a short rest and a snack. But surface intervals are not just about clearing your nitrogen bar or waiting for your computer to give the green light.
If you want to dive more safely, stay sharper, and get more out of your dive days, surface intervals deserve more attention.
What Is a Surface Interval?
Your surface interval is the time between the end of one dive and the beginning of the next. During this time, your body releases some of the nitrogen it absorbed while underwater. The longer the interval, the more nitrogen you eliminate.
Your dive computer keeps track of this, updating your no-decompression limits (NDLs) and estimating your tissue saturation.
But it is only an estimate.
Why the Computer Is Not the Whole Picture
Dive computers use mathematical models to estimate nitrogen loading across a set of theoretical tissue compartments. They do not measure what is actually happening in your body. Two divers doing the same dives may release nitrogen at different rates depending on:
- Age and fitness level
- Hydration status
- Dives completed earlier in the week
- Fatigue, illness, or exposure to cold
In short, computers are valuable tools, but they are not perfect.
The Benefits of a Proper Surface Interval
Aside from basic decompression theory, a solid surface interval helps you:
Lower the Risk of DCS
Even if you stay within your computer’s limits, there is still a risk of decompression sickness (DCS), especially when diving multiple times in a day. A longer surface interval means more nitrogen is released, giving you a greater safety margin.
Feel Better on Your Next Dive
Divers who shorten their surface intervals often feel tired, cold, or uncomfortable on their second or third dive. Giving your body time to warm up, rehydrate, and refuel can make a big difference in how you perform and how good you feel.
Increase Bottom Time Later
A longer surface interval does not just lower risk—it can also increase your no-decompression time on the next dive, allowing you to stay down longer.
Improve Mental Clarity
Your thinking becomes less sharp with fatigue, poor hydration, or excess CO2. Resting at the surface helps you recover, which is especially important if you are leading dives, navigating, or assisting students.
How Long Should a Surface Interval Be?
It depends on your previous dives, your body, and your goals. Here are some general guidelines:
- One hour minimum is often used for recreational dives.
- Ninety minutes to two hours or more is better for deeper dives or days with several dives.
- Longer intervals are especially helpful after demanding profiles or dives with reduced off-gassing like those in cold water.
Tip: Avoid trying to squeeze in maximum dive time by shortening your surface break. You may gain a few extra minutes underwater, but it usually comes with added risk and reduced quality.
Real-World Scenarios
- Liveaboard divers often follow tightly packed dive schedules. Consider skipping one dive each day to give your body more time to recover.
- Shore divers may surface, gear up again, and re-enter too quickly. Plan a longer rest before your next dive.
- Cold water divers experience slowed circulation, which reduces nitrogen release. A longer break is even more important in these cases.
How to Get the Most from Your Surface Interval
- Drink fluids like water or electrolyte solutions.
- Eat something light—focus on carbs and protein instead of greasy food.
- Keep warm, especially if it is windy or cold above water.
- Review your dive log and note how different intervals affect your energy and comfort.
- Relax your mind—chat, write in your logbook, or just rest.