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  • The Shearwater Perdix should be stored in a clean, cool and dry environment.
  • Do not allow salt deposits to build up on your dive computer. Wash your computer with freshwaterto remove salt and other contaminants.
  • Do not use detergents or other cleaning chemicals as they may damage the Perdix dive computer.
  • Allow to dry naturally before storing.
  • Do not wash with high pressure water as it may damage the depth sensor.
  • Store the Shearwater Perdix upright and out of direct sunlight in a cool, dry and dust free environment. Avoid exposure to direct ultra-violet radiation and radiant heat.
  • Do not store batteries in the Perdix for long periods (several months). Batteries can and do leak, so don’t risk your expensive computer on a simple task like removing batteries. Dead batteries are at a higher risk of leaking.

In Gauge Mode the Perdix does not know what gas you are breathing and therefore cannot track the inert gas tissue loading.

Depth is not measured directly. Dive computers measure pressure, and convert this to depth based on an assumed density of water.

Water density varies by type. The weight of salts dissolved in saltwater make it heavier than freshwater. If two dive computers are using different densities of water, then their displayed depths will differ.

The water type can be adjusted on the Perdix. In the System Setup->Mode Setup menu, the Salinity setting can be set to Fresh, EN13319, or Salt.

The EN13319 (European CE standard for dive computers) value is between fresh and salt and is the Perdix default value. The EN13319 value corresponds to a 10m increase in depth for pressure increase of 1 bar.

The density value used for each setting is:

  • Fresh Water = 1000kg/m³
  • EN13319 = 1020 kg/m³
  • Salt Water = 1030 kg/m³

The @+5 (at plus five) feature shows the Time-To-Surface (TTS) in minutes if you were to remain at the current depth for 5 more minutes. The main screen NDL value can be setup to show @+5 once deco is required. The @+5 can be compared against the current TTS to provide a variety of information.

The @+5 can be used as a measure of how fast decompression is accumulating. For example, you could be on a wreck with a scheduled time to meet back at the boat. By looking at the @+5, you can tell how much more deco time staying 5 more minutes on the wreck would cost, and plan accordingly (keeping of course within gas quantity and other limits).

Also, the @+5 value can be used as a rough measure of on or off gassing and the current deco efficiency. For example, say you are decompressing from a deep dive where there is a nice reef at 50 feet. Once the 50 foot stop has cleared, it may not seem too appealing to just head up to the deco line to hang. If you look at the @+5 and it is 4 minutes less than the TTS, then this means you are getting about 80% deco efficiency, so you might decide to hang out to enjoy the reef a little longer. Once the @+5 has drawn equal with the TTS, you are no longer decompressing effectively. This means staying 5 more minutes will make the dive 5 minutes longer, but the deco stops won’t be any longer. This is helpful information in deciding when to head up.

The GF99 value shows the current leading tissue inert gas super-saturation percent gradient as defined by the Bühlmann ZHL-16C decompression model. If that sounds confusing, then recommended reading is Erik Baker’s paper, “Clearing Up Confusing About Deep Stops”.

This value can be used as a rough measure of the current decompression risk. A value of 100% (Bühlmann’s originally allowed super-saturation limit) is now generally accepted to be too risky. The GF low and high conservatism settings are used to scale Bühlmann’s original limits to reduce risk of decompression sickness. The default GF low value of 30% limits the super-saturation gradient at the deepest stop. The default GF high value of 80% sets the surfacing limit. Between the deepest stop and the surface the GF limit is linearly interpolated.

The GF99 value shows the current super-saturation as a percentage of Bühlmann’s original limits. If no super-saturation exists, then the GF99 displays “On Gas”. Once a super-saturation exists, the GF99 is displayed in green. It switches to yellow when the GF99 exceeds the value defined by the GF conservatism settings. Above 100% it is displayed in flashing red.

In extreme conditions, decompression risk can be traded for operational risk by using the GF99 display. For example, in a low-gas situation or perhaps a bailout or injury, you may want to get to the surface faster, but not blow off all the remaining decompression stops. You could then violate the stop displayed by the Predator, and decide to follow a more aggressive GF99, say 95%. This will get you out of the water faster, at a higher risk of decompression sickness, while still remaining within some limits. Upon resurfacing, appropriate action for omitted decompression should be followed such as rest, surface O2, monitoring symptoms and contacting DAN or other diving medicine center.

Conversely, the GF99 value can also be used to add conservatism. For example, if you knew that you had been exposed to factors that increase decompression sickness risk such as exercising during the bottom time or being colder on deco than the bottom, then you could use this value to extend shallow stops. Of course, you could always just add a few minutes to your last stop, but this gives a quantitative measure to correlate with “how you feel” after the dive.

The standard decompression model is Bühlmann ZHL-16C with Gradient Factors. Also, the VPM-B decompression model is available by purchasing an unlock code. More information can be found in the FAQs below.

Recommended reading is Clearing up the Confusion About ‘Deep Stops - Eric C. Baker, P.E.

Yes, the Perdix saves the decompression tissue loading in permanent (non-volatile) memory every 16 seconds when on, and every 5 minutes when off. After a battery change the tissue loading will be restored to the last saved value.

If the battery is removed shortly after a dive but then reinstalled some time (days) later, the residual inert gas loading will be restored even though your body will have returned to equilibrium values. If it has been more than 4 days since your last dive, it is safe to reset the tissues. Otherwise, do not reset the tissues and simply accept the higher conservatism for the next dive. Quick battery changes (battery out less than 10 minutes) do not suffer this problem, and the tissues should not be reset.

Battery Changed

Short Answer:

While almost any kind of AA sized battery works with your Shearwater Perdix, the standard 1.5V alkaline battery (the type found in stores around the world) works best.

Long Answer:

There are numerous types of AA sized batteries that will work in your Shearwater Perdix, read below for more details:


We recommend the AA 1.5V alkaline battery (e.g. the Duracell Coppertop) because it is:
A) Inexpensive
B) Available anywhere
C) Reliable
D) Gives about 45 hours of diving
As an added bonus your Perdix provides a useful “Fuel Gauge” display for these batteries.

LEAKAGE WARNING: Alkaline batteries are prone to leaking, especially when completely discharged. Do not store with a discharged alkaline battery installed.


The Saft 3.6V LS14500 battery (used by the Shearwater Predator) is also a good choice, primarily because it has the longest usable life (130 hours on medium brightness). However they are:
A) Expensive
B) Hard to find
C) Sensitive to temperature and storage conditions
In addition they are incompatible with the new “Fuel Gauge” feature so only three levels are given: Full, Low (Yellow) and Critical (Red).

Li-Ion - Rechargeable

The 3.7V Li-Ion 14500 battery is a good choice that can be purchased online. The AW brand is recommended and typically high quality. The brands Trustfire and Ultrafire can be good, but seem to come from a wider variety of sources and many users report getting duds. The Li-Ion batteries give about 40 hours per charge and are compatible with the new “Fuel Gauge” feature. Note that these batteries are actually about 4.2V when fully charged.

NiMH - Rechargeable

The 1.2V NiMH battery can also be used. These are commonly used in photo flashes and digital cameras, and can be purchased in most electronics stores. About 35 hours per charge can be expected. We recommend using the low self-discharge models typically labeled as “pre-charged”, “ready charged”, “stay charged” etc. and have capacities around 2000mAh. The older style high self-discharge batteries have higher capacities (around 2800mAh) but are not recommended. They will work, but will go dead in a few weeks just sitting on the shelf. Also, all NiMH batteries are incompatible with the new “Fuel Gauge” feature so only three levels are given: Full, Low (Yellow) and Critical (Red). If you have these batteries already from your photo flash, feel free to use them. However we do not recommend buying them for the Perdix as better choices are available.

Photo Lithium 1.5V

These are the best choice for cold water divers. Sold as the Energizer brand Advanced Lithium and Ultimate Lithium batteries. The 1.5V Photo Lithium batteries offer almost double the run time in a Perdix when compared to an alkaline battery. However they can cost about 4X as much as an Alkaline. They are a good choice if you want longer run time than alkaline batteries provide or if diving in waters colder than 8 degrees Celsius (46 degrees Fahrenheit) . They can be found in most department stores or electronics stores and also in many drug stores.

Zinc-Carbon 1.5V

1.5V Zinc-Carbon batteries are el-cheapo batteries commonly found in dollar stores. Although they work, they only provide about 10 to 15 hours and so are not recommended. However if they are all you can get on a tropical island somewhere, feel free to use them. Set the Perdix battery type to “1.5V Alkaline” when using zinc-carbon batteries.

To summarize:

Type Nominal Voltage Approx. Med. Battery Life Rechargeable Availability Cost (USD) Cost (500 hrs)
Alkaline 1.5 V 34 hrs No Excellent $0.75 $11.50
Saft LS14500 3.6 V 90 hrs No Poor $7.50 $42
Li-Ion 3.7 V 34 hrs Yes Poor $12.00 $35*
NiMH 1.2 V 30 hrs Yes Good $5.00 $20*
Photo Lithium 1.5 V 55 hrs No Good $3.00 $27

*For rechargeable batteries, cost for 500 hours of diving is cost of 2 batteries plus charger.

We are sorry that you are having a problem with your dive computer that can't be resolved with our FAQs.  If your dive computer needs some kind of repair, simply email us at info@shearwater.com to initiate the process.

Please include your name, shipping address and phone number, a description of your problem, unit model, S/N and Firmware Version.  We’ll get you an RMA number and instructions on how to send your computer in for repair. Please do not return your computer to us or any of our service centers without an RMA number.

To find your S/N and firmware, turn on your computer (unless it won’t turn on) and from the main screen press the right side button 8-10 times until you see the S/N displayed (lower left) and Firmware (lower right) of the screen.

For full instructions with pictures explaining the best way to remove and replace the O-ring, please click HERE

The downloads for the Perdix are found HERE.

Shearwater has a 2 year warranty on all products. The warranty lives with the unit, not with the original purchaser. This means that whether you buy your unit from our dealer network or second-hand the warranty will still be effective. Once the warranty period has passed computers should be serviced annually at your nearest service center.

It is unnecessary to register your unit upon purchase. Every Shearwater unit is tracked with a unique serial number.

To purchase the VPM-B upgrade you can contact any dealer from our dealer network, provide them with your serial number, and request to purchase the unlock code.

We recommend you remove alkaline batteries from your unit if you intend to store it for an extended period. Alkaline batteries have a tendency to leak when they have fully discharged.

Yes, to unlock dive log recovery, go to “Dive Log->Edit Log Number” and set this to “9997”.


Now the “Clear Logs” menu option will be changed to “Restore Logs”. This will restore all deleted logs. To restore individually, go to the “Dive Log->Display Logs” page. Deleted logs will be grayed-out. Select the dive to restore, then press the right button until the “Edit Dive” menu comes up. This will have a restore option.


Remember to go back to “Edit Log Number” and set it back to its previous value. The next dive # will be the number entered here plus one (e.g. If 2 is entered, the next dive will be dive #3).

Yes, all settings and dive logs are saved in permanent (non-volatile) memory and restored after the battery is changed.

To reset the settings to defaults, use the “System Setup->Reset to Defaults” menu. You can choose to reset the settings, the deco tissues, or both.

When the battery is removed the clock stops running. Upon installation of the battery, the clock is loaded to the last saved value (saved every 16 seconds when on, and every 5 minutes when off).

The Perdix uses a highly accurate quartz crystal for time keeping. A maximum error of about 1 minute per month can be expected. Larger errors are likely due to the clock being stopped while the battery is removed during a battery change.

battery changed clock

After a battery change a screen is displayed that allows quick access to correcting the time. The time can also be corrected in the System Setup menu.

The Perdix will automatically turn-on when submerged underwater. This is based on pressure increase and not on the presence of water (i.e. the Perdix does not have wet contacts).

This feature is supplied as a backup for when you forget to turn on your Perdix. We recommend turning on manually before each dive to confirm proper operation and to double check battery status and setup.


The Perdix turns on automatically when the absolute pressure is greater than 1100 millibar (mbar). It can take up to 15 seconds for the Perdix to activate once 1100 mbar is exceeded. For reference, normal sea level pressure is 1013 mbar and 1 mbar of pressure corresponds to approximately 1 cm (0.4") of water.

So the Perdix will automatically turn-on when about 0.9 m (3 ft) underwater when at sea level. If at higher altitude, then the Perdix auto-on will occur at a deeper depth. For example, when at 2000 m (6500 ft) altitude the atmospheric pressure is only about 800 mbar. Therefore, at this altitude the Perdix must be submerged underwater by 300 mbar to reach an absolute pressure of 1100 mbar. This means the auto-on occurs at about 3 m (10 ft) underwater when at an altitude of 2000 m.

Summary: The guaranteed depth accuracy range is to 130 msw / 425 fsw. However, the case is rated to withstand 260 msw / 850 fsw. The depth sensor will continue to function to this depth, however, at reduced accuracy.

The pressure sensor that is used to determine depth is rated by the manufactured to be calibrated to a pressure of 14 Bar (about 130 msw / 425 fsw). It is designed to withstand pressures up to 30 Bar (290 msw / 950 fsw) . We find the sensors typically meet the EN13319 accuracy of +1m/-1.5m to about 190 msw / 625 fsw. The sensors continue to function to at least 300 msw / 985 fsw .

The Perdix case is rated to a crushing pressure of 260 msw / 850 fsw. The limiting factor is not the strength of the case, but rather the bending of the window inwards which eventually impacts the internal electronics and LCD display. We have tested units to dozens of cycles to 350 msw with no leaking or case failures. However, the window bends enough to impact the LCD, leading to damage or cracking of the display.

The Petrel is rated to a crushing pressure of 300 msw / 985 fsw because of larger internal clearances due to its thicker design. The window thickness, and therefore deflection, is about the same on both the Petrel and Perdix.

No, the Perdix is a stand alone only product.

The Perdix does have a rebreather (CC) mode that uses internal fixed PPO2 setpoints. This is useful for calculating backup decompression schedules when diving a closed circuit rebreather.

The Petrel 2 will continue to be sold in the Fischer and DiveCAN models for connecting to a rebreather.