Oceanic Geo 4.0 Dive Computer: Specifications and Who It Suits
The Oceanic Geo 4.0 is a intermediate tier dive computer at $400 to $500, running Dual algorithm, Pelagic DSAT or Pelagic Z+ with a segment lcd with backlight and no air integration, accepting nitrox mixes up to 100 percent. Divers who want to match a buddy or an operator running a specific algorithm.
The Oceanic Geo 4.0 is a intermediate tier dive computer in the $400 to $500 band. The distinctive Oceanic feature is the dual algorithm: you choose between the liberal Pelagic DSAT and the more conservative Pelagic Z+, which matters if you dive with a buddy on the other model and want your no stop times to match.
The specifications below are the manufacturer's published figures. Where we could not confirm a figure against the maker's own documentation, the row is left out rather than guessed at, which is why some units on this site show fewer rows than others. On a page whose readers can check the work, a missing row is better than an invented one.
What are the Oceanic Geo 4.0 specifications?
| Specification | Geo 4.0 |
|---|---|
| Brand | Oceanic |
| Model | Geo 4.0 |
| Decompression model | Dual algorithm, Pelagic DSAT or Pelagic Z+ |
| Maximum oxygen fraction | 100 percent |
| Air integration | No |
| Display | Segment LCD with backlight |
| Battery | User replaceable |
| Depth rating | 100 m (328 ft) |
| Modes | Air, Nitrox, Gauge, Freedive |
| Trimix | No |
| Closed circuit | No |
| Price band | $400 to $500 |
| Tier | Intermediate |
Who is the Geo 4.0 for?
Divers who want to match a buddy or an operator running a specific algorithm.
An intermediate tier computer is the buy-once purchase. It costs enough to hurt and little enough that you will not replace it, and the features it adds over a beginner unit, usually a better display and a model you can configure, are ones you will still be using in ten years. This is the tier where most divers who dive regularly should be shopping.
Who should not buy the Geo 4.0?
Divers who would rather not have to understand the difference, in which case pick one and leave it alone.
That is the more useful half of any specification page. Computers in this category are close enough on the things that matter, tracking depth and time and applying a model, that the deciding factor is usually a mismatch rather than a ranking: a screen you cannot read without glasses, a menu system nobody near you can teach, or a feature set aimed at diving you do not do. Compare against the alternatives at the bottom of this page before deciding.
What does Dual algorithm, Pelagic DSAT or Pelagic Z+ actually mean on a dive?
A decompression model is a mathematical description of how quickly inert gas moves into and out of body tissue, used to calculate how long you can stay at a depth before a direct ascent stops being acceptable. Every computer runs one, they disagree with each other, and the disagreement is real rather than cosmetic.
Pelagic DSAT descends from the data behind the recreational dive planner tables and sits at the liberal end of the models in common use. It will show longer no-stop times than a conservative RGBM implementation on the same profile. That is not a fault, but it is something to know before you dive alongside a buddy on a different brand, because the pair of you will be looking at meaningfully different numbers and the dive should be run on the more conservative one.
A dual algorithm computer lets you pick which model it runs, usually a liberal option and a conservative one. It is a genuinely useful feature for a diver who buddies with people on other brands, because it lets you match the group rather than argue about whose computer is right. Set it before the dive, not during it, and do not change it between repetitive dives.
Whichever model a computer runs, the rule is unchanged: your own computer supersedes any published table, two computers on the same dive can legitimately disagree, and a buddy pair runs the dive on the more conservative of the two. The algorithm comparison covers the trade in detail, and the no-decompression limits table shows how far apart published figures can be.
What nitrox mixes can the Geo 4.0 handle, and to what depth?
The Geo 4.0 accepts oxygen fractions up to 100 percent. That covers every recreational mix and the oxygen-rich gases used for decompression in technical diving, so the computer will never be the limiting factor.
Maximum operating depth is set by the oxygen partial pressure, not by the computer. MOD in feet of sea water equals 33 multiplied by the maximum ppO2 divided by the oxygen fraction, minus one. The working maximum is 1.4 ata for the bottom phase of a dive, and 1.6 ata is a contingency ceiling used for decompression gas at rest rather than a target to plan against.
| Mix | MOD at 1.4 ata | MOD at 1.4 ata, metric | MOD at 1.6 ata |
|---|---|---|---|
| Air (21%) | 187 ft | 57 m | 218 ft |
| EAN28 | 132 ft | 40 m | 156 ft |
| EAN32 | 111 ft | 34 m | 132 ft |
| EAN36 | 95 ft | 29 m | 114 ft |
| EAN40 | 82 ft | 25 m | 99 ft |
| EAN50 | 59 ft | 18 m | 73 ft |
| EAN80 | 25 ft | 8 m | 33 ft |
| EAN100 | 13 ft | 4 m | 20 ft |
Run your own mix and your own planned depth through the nitrox MOD calculator, and pair it with the equivalent air depth calculator, which handles the nitrogen half of the same decision. MOD is an oxygen limit and EAD is a nitrogen calculation, and a nitrox dive is only planned when you have both.
Whatever the computer accepts, you analyse every fill yourself with an oxygen analyser , sign for it, and set the mix on the computer before you get in. A computer set to air on a nitrox fill is merely conservative. A computer set to EAN36 on an air fill is dangerous, because it will show you no-stop time you do not have.
Does the display suit the diving you do?
The Geo 4.0 uses a segment lcd with backlight. Display technology decides legibility more reliably than screen size does, and legibility is the specification that actually matters at depth.
A segment display shows fewer things at once and shows them very large, which is a real advantage rather than a compromise. Big digits are readable through a fogged mask and without reading glasses, and a segment screen sips power, which is why these units run for a year or more on a user replaceable cell. What you give up is the ability to show a graph or to signal a warning with colour.
Whatever the screen, check one thing in the shop before you buy: can you read it at arm's length without your glasses, in dim light, at a glance? Presbyopia arrives for most divers in their forties and it is the single most common reason a computer gets replaced.
How does air integration work on this unit?
The Geo 4.0 has no air integration. Cylinder pressure comes from a mechanical submersible pressure gauge on a hose, which is the standard recreational arrangement and is entirely adequate: it needs no battery, no pairing and no line of sight. If pressure on the wrist is the feature you want, the answer is a different computer rather than an accessory, and the air integrated roundup covers the options.
Air integration does not change how much gas you have or how fast you use it. That is your own respiratory minute volume, and it is worth knowing as a number rather than as a feeling. The SAC rate calculator works it out from one logged dive, and the gas planning calculator turns it into a reserve and a turn pressure.
The Geo 4.0 also carries a freedive mode, which tracks depth and time on breath-hold descents and warns on ascent rate. Useful if you spearfish or freedive on the same trips, and worth knowing that mixing breath-hold diving with scuba on the same day carries its own risks that a mode selector does not address.
Gauge mode turns the computer into a depth and time instrument with no decompression calculation at all. It exists for divers running their own tables or their own plan, and it is not a way to dive past a no-stop limit without the computer complaining. Using it that way is technical diving without the training, and it is the single most common misuse of the mode.
How does it compare with the rest of the Oceanic range?
| Model | Tier | Display | Air integration | Price band |
|---|---|---|---|---|
| Veo 4.0 | Beginner | Large segment LCD | No | $300 to $400 |
| Pro Plus 4.0 | Expert | Large segment LCD with backlight | Included | $850 to $1,000 |
| Pro Plus X | Expert | Full colour LCD | Included | $1,000 and up |
Staying inside one brand has a genuine advantage that specification tables hide: the menu logic, the app and the transmitter all carry over, and a shop that services one unit usually knows the others. That matters most for air integration, where the transmitter is locked to the ecosystem.
What else should you look at in the same tier?
| Model | Brand | Algorithm | Price band |
|---|---|---|---|
| Michelangelo | Cressi | Cressi RGBM | $300 to $400 |
| i200C | Aqua Lung | Pelagic Z+, based on Bühlmann ZHL-16C | $320 to $400 |
| Quad | Mares | Mares-Wienke RGBM | $350 to $450 |
| Luna 2.0 | Scubapro | $350 to $450 | |
| D4f | Suunto | Suunto RGBM | $400 to $550 |
| Descent G1 | Garmin | Bühlmann ZHL-16C with Gradient Factors | $400 to $500 |
What should you check before you buy?
- Can you read it? At arm's length, in dim light, without glasses. This is the most common reason a computer is replaced, and no specification captures it.
- Can someone near you teach it? A unit your local shop rents and services is worth more than a slightly better one nobody around you has used.
- Does the battery arrangement suit your travel? A user replaceable cell is a ten minute fix on a trip, and a hatch you have to close correctly every time.
- Is the price band real for you? This is the middle of the market, which is where most divers who dive regularly should be shopping.
- Are you buying capability or permission? A computer that supports trimix does not qualify you to dive it. Training comes first, always.
Related reading
Frequently asked questions
Does the Oceanic Geo 4.0 support nitrox?
Yes. The Geo 4.0 accepts oxygen fractions up to 100 percent. That covers every recreational nitrox mix and the oxygen-rich decompression gases used in technical diving, so the mix setting will never be the limiting factor on a recreational dive. Remember that the computer accepts a number you type in: you still analyse every fill yourself, verify the actual fraction with an analyser, and set the mix before you dive. On EAN32 at a 1.4 ata working limit the maximum operating depth is 111 feet.
What decompression model does the Oceanic Geo 4.0 use?
The Geo 4.0 runs Dual algorithm, Pelagic DSAT or Pelagic Z+. Pelagic DSAT is at the liberal end of the models in common recreational use, so it will give longer no-stop times than a conservative RGBM implementation on the same profile. That is worth knowing before you dive it alongside a buddy on a different brand. Whatever the model, your own computer supersedes any published table.
Does the Oceanic Geo 4.0 have air integration?
No. The Geo 4.0 has no air integration, so cylinder pressure comes from a submersible pressure gauge on a hose. That is the standard recreational arrangement and it is entirely adequate. If tank pressure on the wrist is the feature you want, you are shopping for a different unit rather than a different accessory.
What kind of battery does the Oceanic Geo 4.0 use?
User replaceable. A user replaceable battery means a dead cell on a dive trip is a ten minute fix with a coin and a fresh o-ring rather than a shipped service. The trade is a hatch with a seal, which is one more thing to flood if it is closed carelessly or the o-ring is dirty. Change it before a trip rather than during one.
How deep is the Oceanic Geo 4.0 rated?
The Geo 4.0 carries a published depth rating of 100 metres, about 328 feet. That is far beyond any recreational limit and reflects technical capability rather than an invitation. A depth rating describes the pressure the housing survives, not a depth you are qualified to dive. The recreational limit is 130 feet, and going past it requires training that this site does not substitute for. Treat the rating as a durability specification.
Is the Oceanic Geo 4.0 a good choice for a new diver?
It can be, if you intend to keep it. At $400 to $500 it is more computer than a first fifty dives requires, but it is also a unit you will not replace, which is the argument for buying it early. Divers who would rather not have to understand the difference, in which case pick one and leave it alone.
How we choose: we compare published manufacturer specifications, published training agency standards, and verified owner reviews across retailers. We do not test gear in person, and every depth rating, cylinder capacity and algorithm name quoted here is the manufacturer's published figure unless we say otherwise, so confirm it on the current spec sheet before you buy. Nothing here is dive instruction, and no calculator output on this site is a dive plan. Scuba diving carries a real risk of decompression sickness, oxygen toxicity, barotrauma and drowning. Dive within the limits of your certification, verify every plan with your own computer, and buy the training before the gear that assumes it.
Logging your own SAC rate and gas plans? The Dive Kit & Air Planning Workbook is the paid version of these pages: 8 printable worksheets you fill in with your own numbers, plus the full PDF, $29.