Discover what no stop time (no-decompression limit) means in scuba diving, how it’s calculated, and why every recreational diver must understand it for safe dive planning.
In scuba diving, no stop time is the maximum amount of time you can stay at a given depth and still ascend directly to the surface without making any mandatory decompression stops. This limit is also known as the no-decompression limit (NDL) or no-stop limit, and it defines whether a dive is considered a standard recreational "no-stop dive" or a decompression dive.
On a no-stop dive, you can ascend continuously (usually with a 3–5 minute safety stop at 3–5 metres/10–15 feet) and still keep decompression sickness risk within accepted recreational standards. Once you exceed the no stop time for your depth, decompression stops become mandatory, and you enter decompression diving, which requires specialized training, planning, and equipment.
Most training agencies treat no stop time and no-decompression limit as two names for the same concept: the time you can spend at a given depth without mandatory decompression stops. Traditional dive tables, such as those based on Bühlmann or U.S. Navy models, list NDLs for different depths, while modern dive computers calculate and display your remaining no stop time in real time during the dive.
Historically, many agencies used the term "no-decompression limit" (NDL), but some recreational programs now prefer "no stop limit" to emphasize that decompression is always happening in your body — what changes is whether decompression stops are required. In practice, divers use NDL and no stop time interchangeably to mean the same operational limit for recreational dives.
When you descend, the pressure increases and your body absorbs more nitrogen from your breathing gas; the deeper and longer you stay, the more nitrogen your tissues take on. No stop time is calculated so that, if you ascend at a controlled rate from that depth, the nitrogen supersaturation in your tissues stays within limits considered acceptable for a direct ascent without mandatory stops.
For example, common recreational tables and computers give a no-decompression limit of about 55–56 minutes at 18 metres/60 feet on air for a first dive of the day. If you stay within that limit, you can ascend directly (plus a recommended safety stop) and still keep decompression sickness risk relatively low; go beyond it and you must complete decompression stops at specific depths and times to reduce that risk.
Recreational training agencies design entry-level and advanced recreational courses around no-stop diving, leaving planned decompression dives to specialized technical training.
No stop times are derived from decompression models that approximate how inert gas (mostly nitrogen) dissolves into and leaves body tissues under pressure. Early models, like those from Haldane and later Bühlmann, led to printed dive tables listing maximum no-decompression times for each depth, such as the Bühlmann 86 tables used widely in Europe.
Dive tables show, for each depth, the maximum bottom time you can spend while still making a direct ascent without required decompression stops; exceeding those depth–time limits pushes the dive into decompression territory. For instance, sample Bühlmann-based tables list no-stop limits such as 35 minutes at 21 metres and 25 minutes at 24 metres on air, with significantly shorter limits at deeper depths.
Most divers today rely on dive computers, which continuously track your depth and time and compute remaining no stop time using an internal decompression algorithm. The computer updates your NDL every few seconds, reflecting multi-level profiles, current depth, and residual nitrogen from previous dives.
Your display typically shows both current depth and a countdown-like value labelled NDL or no-stop time; as you stay deeper or extend your dive, that number decreases. Ascending to a shallower depth often increases your available no stop time, because decompression models treat shallower segments as an off-gassing phase that reduces tissue loading.
Several variables influence how much no stop time you have on any given dive:
Understanding how these factors interact helps divers plan profiles that stay well within no stop time margins rather than skirting the absolute limit.
Even on a no-stop dive, agencies and instructors strongly recommend a 3-minute safety stop around 3–5 metres/10–15 feet at the end of the dive. A safety stop is not part of the formal decompression obligation but adds an extra buffer, giving your body more time to off-gas nitrogen and further reducing decompression sickness risk.
Divers are often taught that, for example, a 55-minute dive to 18 metres/60 feet is still within the no-decompression limit, regardless of whether a safety stop is made, though skipping the stop is discouraged in normal conditions. Think of the safety stop as a simple, low-cost habit that builds extra safety into every no-stop dive.
If your dive exceeds the no stop time for your maximum depth, you move into decompression diving and must complete one or more decompression stops. These stops occur at specific depths and durations calculated by your computer or decompression tables, and skipping them greatly increases the risk of decompression sickness.
Unlike safety stops, decompression stops are mandatory; you cannot safely ascend directly to the surface once your computer indicates a required stop without accepting a significant spike in decompression risk. This is why recreational training emphasizes staying comfortably within no stop time and avoiding planned decompression without proper technical training.
Divers can manage no stop time more safely and effectively by applying a few practical habits:
By understanding what no stop time is and how it works, recreational divers can plan safer dives, make smarter decisions underwater, and dramatically reduce their risk of decompression-related injury.