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Planning
Submersion's Planning hub gathers the tools you use before a dive: a full multi-level dive planner, an interactive decompression calculator, a set of gas calculators, a weight estimator, and a surface-interval tool for repetitive diving. Everything runs on your device with no account or connection required.
Note
Where to find it: Open Planning from the navigation rail (or the bottom navigation bar on a phone). On a phone you land on a list of the five tools; on a tablet or computer the hub uses a master-detail layout, with the tool list on the left and the open tool filling the rest of the screen.
Warning
These tools are for planning purposes only. Always verify their numbers against your training and run every dive on a dive computer. The decompression figures come from a software model (Bühlmann ZH-L16C) and can differ from what your computer shows. Submersion is not a substitute for a dive computer or for proper training.
The Planning hub opens to a list of five tools. The rest of this page covers each one in the order you meet it:
| Tool | What it answers |
|---|---|
| Dive planner | "What does this whole dive look like — depths, gases, deco, and gas use?" |
| Deco calculator | "At this depth on this gas, how long is my no-stop time, and what stops do I owe?" |
| Gas calculators | "What's my MOD, best mix, gas use, reserve, or narcotic depth?" |
| Weight calculator | "Roughly how much lead should I start with for this exposure suit and tank?" |
| Surface interval | "How long must I wait before my next dive?" |
Note
Each tool keeps the values you enter while you move between them, but those values are not saved when you leave the Planning area or close the app — the planning tools are live calculators, not stored records. To keep a dive in your log, enter it through Dive logging instead.
The dive planner is the most complete tool here. You build a dive out of segments — descent, bottom, ascent, gas switches, and stops — choose your tanks and gas mixes, and Submersion runs the whole profile through the decompression model to show you the stops you owe, your runtime, and how much gas each tank will use.
It is organized into three tabs:
- Plan — where you set everything up.
- Results — the decompression schedule and gas projections, with a badge showing how many warnings the current plan raises.
- Profile — a depth-versus-time chart of the dive you have built.
If you just want a simple square-profile dive, tap Quick Plan in the top bar. Enter a maximum depth (5–40 m / 16–131 ft) and a bottom time (5–120 minutes), and Submersion builds a complete profile for you: a descent, the bottom segment, an ascent, and a 3-minute safety stop at 5 m (16 ft). You can then fine-tune any of those segments on the Plan tab.
The Plan Settings panel at the top of the Plan tab holds the parameters that apply to the whole dive:
- GF Low / GF High — the gradient factors that set how conservative the decompression model is, each adjustable from 10 to 100. Gradient factors (GF) scale how close the model lets your tissues approach their theoretical limits: a lower number is more conservative. They start from your app settings (GF 50/85 by default). See Glossary for a fuller explanation.
- SAC rate — your surface air consumption (SAC), the volume of gas you breathe per minute at the surface, adjustable from 8 to 30 L/min. This drives the gas-use projections.
- Altitude — set this above sea level for an altitude dive; the planner accounts for the thinner atmosphere.
- Dive site — optionally attach a site from your dive sites.
Tip
If you do not know your SAC rate, Submersion can estimate it from dives you have already logged — see Statistics. A realistic SAC is what makes the gas-consumption and reserve numbers meaningful.
In the Tanks list you add one or more cylinders, each with:
- a name,
- a volume in litres,
- a starting pressure in bar,
- a gas mix, set by its oxygen (O₂) and helium (He) percentages, and
- a role — back gas, bottom deco gas, stage deco gas, or bailout.
A new plan starts with a single aluminium-80 (≈ 11.1 L) tank filled to 200 bar on air (21% O₂). Add a second tank with a richer mix — for example EAN50 (50% O₂, a nitrox blend) — and you can switch to it partway through the dive to shorten your decompression.
A dive is a sequence of segments, which you add, edit, reorder, and remove in the Segments list. Each segment is one of:
- Descent — from one depth down to a deeper one, at a chosen rate (default 18 m/min).
- Bottom — time held at a fixed depth.
- Ascent — up to a shallower depth, at a chosen rate (default 9 m/min).
- Deco stop — a fixed depth held for a set time.
- Safety stop — typically 3 minutes at 5 m (16 ft).
- Gas switch — change to another tank.
Because each segment carries its own start and end depth and its own tank, you can build true multi-level profiles and switch gas at any point in the dive.
Open the Results tab to see what your plan produces. The Decompression section reports:
- Runtime — total planned time, including stops.
- NDL / Status — your remaining no-decompression limit (NDL), or DECO once the plan crosses into a decompression obligation.
- TTS — time to surface, the minutes needed to ascend and clear all stops from the deepest point.
- Ceiling — the shallowest depth you may safely ascend to right now.
- A Decompression Schedule listing each stop's depth, duration, and gas.
The Gas Consumption section shows, per tank, how much gas the dive uses, the pressure remaining at the end, and how much of the tank that represents. If a tank is projected to drop below its reserve, it is flagged.
Submersion also tracks your oxygen exposure across the dive — central nervous system toxicity (CNS, shown as a percentage of the daily limit) and oxygen tolerance units (OTU) — and raises a warning for anything worth your attention: ppO₂ (the partial pressure of oxygen) above 1.4 bar or 1.6 bar, an exceeded NDL, high CNS or OTU, an ascent rate that is too fast, a high equivalent narcotic depth (END), a gas dropping below its minimum reserve, or a depth beyond a gas's maximum operating depth (MOD). The warning count appears as a badge on the Results tab.
Note
The dive planner is a live planning tool. The Save Plan and Convert to Dive actions in the menu are not yet wired up — selecting them only acknowledges the action and does not store a plan or create a logged dive. Treat the planner as a worktable you recalculate as you experiment, and log the dive you actually make through Dive logging.
The deco calculator is a faster, single-screen alternative to the full planner. It answers one question instantly: for a square dive to a given depth on a given gas, what is your no-stop time, and what do you owe if you overstay it?
Set three things with sliders:
- Depth (default 18 m / 59 ft),
- Bottom time (default 30 minutes), and
- Gas mix — pick a preset (Air, EAN32, EAN36, EAN50, or pure O₂) or open the advanced selector for a custom blend, including trimix (a helium–oxygen–nitrogen mix) with O₂ from 18–100% and He from 0–65%.
As you move the sliders, the results update live: your NDL, ceiling, TTS, the tissue loading across all 16 model compartments, and any deco stops. A gas panel shows the mix's MOD and END and warns you if your chosen depth exceeds the MOD, if ppO₂ is too high, or if the mix is hypoxic (too little oxygen to breathe safely at the surface).
The calculator uses the gradient factors from your app settings (see Settings), so it reflects your personal conservatism. When a result looks useful, tap Add to Planner to carry the depth, time, and gas into the full dive planner and keep building.
Tip
Lower oxygen lets you go deeper before hitting the MOD but shortens your no-stop time; richer nitrox does the opposite. The deco calculator is a quick way to feel that trade-off before committing to a plan.
The Gas Calculators screen is a set of five tabbed tools for the gas-planning arithmetic divers do by hand or on a slate. Each tab is independent; the refresh button in the top bar resets them all to their defaults.
Enter a gas's oxygen percentage and a ppO₂ limit (1.2, 1.4, or 1.6 bar), and the calculator returns the maximum operating depth (MOD) — the deepest you may breathe that gas before its oxygen partial pressure becomes unsafe. As a reminder: a lower oxygen fraction gives a deeper MOD but a shorter no-stop time.
The inverse of MOD. Give a target depth and a ppO₂ limit, and Submersion returns the richest oxygen percentage you can safely breathe there — the nitrox blend that maximizes your no-stop time without exceeding your oxygen limit. A reference list shows the MOD of the common mixes (Air, EAN32, EAN36, EAN40, EAN50, and pure O₂) at your chosen limit.
Enter an average depth, a dive time, your SAC rate, and a tank size, and the calculator estimates the total gas the dive will consume, the pressure that represents in your tank, and what would be left over — flagging the case where the dive would exceed the tank's capacity.
The rock-bottom reserve is the minimum gas you must keep in hand to get both you and a buddy safely to the surface from depth. Enter the depth, an ascent rate, your SAC and a buddy's SAC, the tank size, and whether to include a safety stop. Submersion applies elevated (stressed) breathing rates, assumes both divers share one tank, and returns the pressure and volume you should treat as your turn-around point. Turn the dive before you reach it.
This tab handles gas narcosis, which matters most on deep air and trimix dives. Set the mix's oxygen and helium percentages, your END limit (the deepest narcotic effect you are willing to accept, default 30 m / 98 ft), and whether to treat oxygen as narcotic (on by default, which is the more conservative assumption). The calculator returns:
- the maximum narcotic depth (MND) — the deepest you can go on that mix before narcosis exceeds your END limit, and
- the equivalent narcotic depth (END) at any depth you set — the air-depth whose narcotic effect matches your mix there.
Adding helium to a mix pushes the MND deeper, which is exactly why trimix is used for deep diving. See Glossary for MOD, END, MND, ppO₂, and the gas abbreviations used here.
Note
The Planning hub's summary still describes "four" gas calculators from an earlier release; the screen itself now has the five tabs above, including MND/END.
The weight calculator gives you a starting estimate for how much lead to carry, so a checkout or weight check begins in the right neighbourhood rather than from scratch. Choose:
- an exposure suit — No Suit, Rashguard Only, 3 mm Shorty, 3 mm Full Wetsuit, 5 mm Wetsuit, 7 mm Wetsuit, Semi-dry Suit, or Drysuit;
- a tank material — aluminium, steel, or carbon fibre (or leave unspecified);
- a water type — salt, fresh, or brackish (or leave unspecified); and
- optionally your body weight.
Submersion combines a base figure for the suit's buoyancy with adjustments for the tank, the water, and your body weight, and shows a recommended weight in your preferred unit (with the other unit in parentheses). A breakdown explains where the number comes from.
Warning
A calculator cannot replace an in-water weight check. Use this figure as a starting point, then confirm your weighting in the water — neutrally buoyant at a safety stop with a near-empty tank — and record what actually worked on the dive. Your gear and exposure suit live in Equipment.
When you plan a second dive in a day, the surface-interval tool tells you how long to wait. It models how your tissues off-gas at the surface and finds the minimum surface interval that keeps your planned next dive within its no-decompression limit.
Enter three things:
- First dive — the depth, time, and gas mix (oxygen and helium percentages) of the dive you just made.
- Second dive — the planned depth and time of your next dive (modelled on air).
- Current interval — a slider, from 0 to 4 hours, for how long you have been on the surface so far.
The tool then shows:
- the minimum surface interval required before the second dive,
- whether your current interval is already enough (a green "safe to dive" or a red "not yet safe" indicator), and
- the NDL for the second dive once you have waited long enough — or "in deco" if that depth and time would put you straight into a decompression obligation.
A tissue recovery chart plots all 16 model compartments off-gassing over the four-hour window, grouped into fast, medium, and slow tissues, with the leading (most saturated) compartment highlighted. A NOW marker shows your current interval and a MIN marker shows the minimum required, so you can see at a glance how much longer you have to wait.
Note
Like the deco calculator, this tool uses the Bühlmann ZH-L16C model with your gradient-factor settings. Its results are estimates for planning and may differ from your dive computer, which is the device you should actually follow between dives.
- Dive logging — record the dive you actually made
- Dive computer — download real profiles instead of planning by hand
- Settings — set the gradient factors and units these tools use
- Glossary — MOD, END, MND, GF, ppO₂, SAC, and the other terms used here
Getting Started
Logging Your Dives
Your Dive World
Diver & Gear
Insights & Planning
Setup & Data
Reference