Successive Dives Planner

Successive Dives — Key Features

• Plan sequences of multiple dives with surface intervals
• Calculate residual nitrogen loading between dives
• Determine NDL for each subsequent dive
• Suggest minimum surface intervals for desired profiles
• Suggest maximum depth or time for your next dive
• Based on Bühlmann ZH-L16C with configurable gradient factors

Successive Dives — How It Works

Enter your dive sequence — depth, time, gas mix, and the surface interval between each dive — and the planner replays each dive on the Bühlmann ZH-L16C model, carrying residual inert-gas tension from one dive into the next. Tissues off-gas during the surface interval at different rates: fast compartments (4-10 minute half-times) clear in under an hour, while slow compartments (240-635 minutes) need many hours to a full day to return to surface saturation. This residual nitrogen shortens the next dive's no-decompression limit — the deeper or longer the first dive, the more pronounced the effect. Three modes let you work from different angles: verify a fixed sequence (will this 3-dive plan stay within NDL?), suggest the minimum surface interval needed before a planned dive, or find the safe depth/time envelope for an upcoming dive given current loading. Treat the output as a planning aid and let your computer track loading in real time on the day itself.

Why Use Our Successive Dives Planner?

• Safely plan multi-dive days without guesswork
• See exactly how residual nitrogen affects your next dive
• Multiple planning modes for different scenarios
• Based on proven decompression algorithms

Successive Dives — Frequently Asked Questions

Why does residual nitrogen matter?

Residual nitrogen carries over between dives because tissues do not fully off-gas during a surface interval — they continue to release the inert gas absorbed on the previous dive at a rate determined by each compartment's half-time. A short interval leaves significant residual nitrogen, which adds to the loading of the next dive and shortens its no-decompression limit. Ignoring this is one of the most common ways recreational divers exceed safe limits on the second or third dive of a day. The planner shows exactly how each dive affects the next.

What planning modes are available?

Three modes cover the typical questions: Verify (does this fixed sequence of dives stay within NDL?), Surface Interval (what is the minimum interval needed before a planned dive to keep it within NDL?), and Envelope (what depth/time combinations are safe for the next dive given current tissue loading?). Use Verify when planning a known itinerary, Surface Interval when scheduling a second dive of the day, and Envelope when you arrive at a site and choose your profile based on conditions.

How many dives can I plan in sequence?

The planner supports unlimited dives in sequence — useful for multi-day liveaboard itineraries, three-tank charters, or week-long technical diving expeditions. In practice, the conservative limit is set by the slow tissue compartments (240-635 minute half-times) that accumulate residual nitrogen across many days and need ~24 hours to fully clear. The planner shows residual loading per compartment so you can see when slow tissues are approaching saturation — common after 4-5 days of repetitive diving without an off day.

What algorithm is used for residual nitrogen?

The successive-dive calculator uses the same Bühlmann ZH-L16C model as the single-dive planner, applied continuously across multiple dives with surface intervals. Each surface interval is computed as an off-gassing phase with breathing air at 1 ata: fast compartments clear in under an hour, slow ones in many hours. There is no separate 'residual nitrogen time group' (RNT) approximation as found in older table-based methods — every tissue compartment is tracked explicitly, which is more accurate for technical, deep, or long dives.

What is the minimum recommended surface interval?

There is no universal minimum — it depends entirely on the first dive's depth and time, and the gas tension still loaded in the slow tissue compartments. As a rule of thumb, conservative recreational practice suggests at least 1 hour between repetitive dives, 2-3 hours after a deep dive (>30 m), and 12-24 hours before flying. The Surface Interval mode of the planner computes the actual minimum for your specific dive sequence using the Bühlmann model, which is always more accurate than any thumb-rule.

Can I plan repetitive dives over multiple days?

Yes — the planner handles repetitive diving across multiple days, which is critical for liveaboards and dive holidays where slow-tissue loading accumulates. After a day of diving, slow compartments (240-635 min half-times) need many hours to a full day to return to surface saturation. The planner models this explicitly: if you log every dive with its surface interval (including the overnight rest), it will show you how multi-day loading affects each successive day's NDLs and recommended margin.

→ How to Plan a Nitrox Dive — A 5-step recreational workflow — pick the blend, know your gas, stay inside NDL

→ Diving Glossary — Essential acronyms and concepts every diver should know