Everybody’s first dive will forge its individual experience deep into the memory bank of that diver. The interesting thing I have realized was that many of those who learn and master cold water diving (perhaps with years of dives) have anxiety for diving in warm water. While the same goes for warm water divers who are reluctant about putting on those layers and added weight and who usually avoid the cold temperatures all together.

So, let’s deep dive into some of the differences of cold and warm water diving, and find out what you need to consider when preparing for cold water diving!

First, Why the Anxiety?

Like changing jobs, many people feel as if they are going to have to start from scratch and be new all over again. Well, hate to break it to you. That’s exactly what is going to happen when changing from diving in cold water to warm water, and vice versa.

It’s time to get off that high horse and add a bit of humility because you may find that a diver with 30 dives in the environment you’re venturing into is much more comfortable than you, with perhaps hundreds of dives in the alternative. It may only take a few dives to figure it out but you still need to forget a bit of what you know and alter it for the environment you’re now in.

I’ll sweat to death!

Yep, number one on a cold water diver’s concern is that they layer up so much and are comfortable in 6°C/43°F or less water, that they fear they’ll die of heat exhaustion in anything above 20°C/68°F!

One thing to remember is that water conducts heat away from your body 20 times faster than air. So, as you increase your exposure to the water by reducing your thermal protection to possibly only a rash guard then the longer you are in the water you will likely not overheat. You may even become cold in 29°C/84°F after 40 minutes of diving. So start with what is recommended by the local dive professional and see how you feel at the beginning, during and after your dive and change it accordingly.

Read More: How Does a Drysuit Work?

It’s too damn cold for me!

Yep, cold water is cold. Otherwise it wouldn’t be called “cold water diving”. Typically, it means anything below 14°C/75°F (Note: Cold water regulator distinction is rated to EN250 EU standard for anything below 10°C/50°F that could have more potential for a free-flow at depth).

But with the proper planning in thermal protection you will be able to enjoy any temperature you plunge into. Now let’s talk head to toe about the thermal gear going from warm into cold because, yeah, this is the big difference there.

Cold Water Diving Gear

Cold Water Diving Hoods

You lose the majority of your heat from your head, likely because of all that thinking you do. So in warmer waters it may be optional but in cold water a hood is mandatory. You forget your hood, you ain’t diving.

Correct fit is important as to keep the trapped water tight to your skin and all that brain activated heat keeping you warm. If your hood doesn’t fit correctly or the upper skirt of your mask isn’t covered by the hood properly you may end up with what can only be described as an “ice cream headache”. Not fun and it could last for hours after the dive. So make sure to have that sorted before you take your gear to the open water.

Diving Mask

Your scuba diving mask is as important as any gear in your kit. Aside from the obvious benefits and necessity of having a mask I’m just going to explain a bit of how to prep your mask. Make sure it fits. A good seal is more important than the brand. You could have the sexiest and most expensive mask ever made but if it don’t fit it ain’t gonna work for you. Next, would be how to prevent the mask fogging.

Masks fog up when the temperature inside the mask is significantly different to the temperature outside of the mask. For example; your warm breath against the cold glass.

Initially, when you buy your mask from your local dive shop each mask is conditioned with a protective coating by the manufacturer. You’ll need to remove this otherwise it will fog up constantly. So prepare your mask the night before your dive. What you need is basic white toothpaste (not gel) and baking soda. Mix these two ingredients and rub that mixture with your finger to spread it on the inside lens of the mask. Then wash it out prior to your dive.

Read More: Pro Tips to Stop Your Mask Fogging Up!

Our recommendation before every dive is to treat the mask with anti-fog or good ole fashioned spit on the inside of your mask. Leave this ‘goo’ until the last moment that you put the mask on.

In cold water you will want to plunge your face into the water you’ll be diving in to get it close to the temperature of the water. BRRRR. Then rinse out that goo with the water you’ll be diving in.

Finally, put the mask on and make sure there’s no forehead exposed and the hood covers that top skirt of the mask. Additionally, don’t over-tighten that mask with the strap. The mask is meant to fit with a good seal. So if fitted properly it will vacuum onto your face on its own. The strap is there to hold it on and not to tighten the mask to your face.

Cold Water Scuba Diving Regulator

One thing to consider when venturing into the cold is “Will my regulator be safe?”

A regulator you bought at a resort in the tropics likely won’t cut it when plunging into the cold water. Why? Because, chances are they’re unbalanced and not environmentally sealed.

This means the regulator can breathe hard at depth (like sucking through a long straw) or even worse, freeze up and free-flow if you end up in waters that a polar bear frolics in for fun. I would strongly suggest not skimping out on a “cheap” regulator when purchasing. Even if you don’t plan to ever dive in the cold; you never know what lies in your diving adventures and you don’t want to have to fork out that dough again if you can prevent it.

Consider buying a cold water diving regulator that is balanced and sealed. Remember, this is your life support system. A hardy regulator made for cold water diving will be versatile (and safe) for diving in both cold waters and warm waters. Be sure you have a good one from the start and service it as the manufacturer recommends to keep it well maintained. So buying a reg that can withstand harsher conditions will most certainly be fine in any condition the tropics will present. They make regs like this that are light-weight, relatively inexpensive and pretty much “bulletproof” to most conditions.

Drysuits and Wetsuits

With cold water diving, you will certainly need a warm exposure suit. If the temperatures are going below 14°C/57°F you should look into a 7mm neoprene wetsuit, a semi-dry neoprene wetsuit or a drysuit (neoprene or membrane).

Neoprene adds buoyancy so that will also decide how much weight to use (We’ll talk about this later). The difference between a wetsuit and a semi-dry are mainly the seals and the zipper. While both require water to flood the suit (Note: the initial flood does suck in the cold) neoprene is incredible for not allowing water to penetrate through it. It’s essentially engineered closed-celled rubber. The water enters through the seals, usually with your help, and does not seep in or out through the neoprene, as many assume that that’s how water enters the suit. Meaning it traps the water from circulating and your body heat keeps that trapped water warm. So the seals of the semi-dry should be tight and snug and the suit should be as close to your body to heat up as little water as possible. So make sure the thing fits you like “Flanders’ ski suit” and could make you bashful in the company of others.

A proper semi-dry has a similar zipper to a drysuit where it allows zero water seepage when secured. The drysuit zipper uses the same technology as an astronauts suit zipper and makes it air tight.

A wetsuit does not have this “air tight” mechanism and can allow some water transfer that may cool you down over a dive.

Drysuits basically trap air into the suit via an inflator hose keeping you nice and dry and toasty. Though you should take note that you’re still submerged underwater for a good period of time so a drysuit isn’t 100% dry. Contributors to getting wet inside your suit are sweat, warm body temperature colliding with the cold water temperature outside may cause condensation or you may move in your seals like looking around with your neck instead of your body allowing water to trickle in. Or worst case you get a tear in your seal or a puncture in your suit (Also note: you should seek training in order to safely and effectively use a drysuit).

A neoprene drysuit adds thermal protection but still adds buoyancy whereas in a membrane drysuit it’s only the underwear you are required to wear that keeps you warm that may add to the buoyancy. A membrane drysuit gives you zero thermal protection. Basically it’s a fashionable garbage bag.

Dry Gloves

Same as a hood. Don’t have gloves? Then you ain’t diving in the cold, my friend. They can be wet or dry but I personally enjoy a dry glove with a nice thermal liner. In wet gloves your hands may get numb after a long dive in the cold even if they fit like a “glove.” The thicker the glove the more difficult it is to move your fingers, however. If using a 7mm glove or thicker you should opt for “lobster” 3-fingered gloves for better dexterity in a wet glove.

Diving Booties and Boots

Booties are great with a wetsuit but boots are required on a drysuit. Booties give you the same thermal protection as a wetsuit so it’s good to have fitting un-holey ones. They range from 2mm-7mm and you should purchase them accordingly based on the type of diving you’ll be doing.

Diving boots are designed to either go over neoprene socks attached to a drysuit or the boots themselves are attached to the drysuit In a bootie they can typically be used with any of your warm water fins. A boot will be larger and require a larger fin size to fit them. 

Fins

As stated above, booties vs boots require a different sized fin. So if you wear a medium fin (9-11US/42-45Uk) you may need to buy or rent a fin size of XXL to fit your boots.

Fins are always subjective as far as style but I prefer more robust and sturdy fins for cold water because you make less movements in the additional gear and weight you require in these waters.

Cold Water Diving Weights 

Ok, now let’s talk about weight. The point of diving is to be submerged underwater for a good period of time. You need to stay down. How much weight you need for this is determined by what you are wearing. In warm water you may only have a 2mm vest or a rash guard or simply “nothing at all” where 4-6lbs/ 2-3kgs will be sufficient.

In cold water diving, you could be wearing 7mm neoprene or more which could bring that amount to nearly 50lbs/22kgs. So how you add weight is crucial by using a weight belt, a heavier steel tank vs aluminum, a weighted standard tank adapter, trim pockets or most people will use their integrated weights on your bcd. Weighting and the positioning of the weight will change as you configure your gear to the type of diving you do.

Try our Scuba Diving Weight Calculator to figure out how much weight you should use!

Buoyancy Compensating Device (BCD)

This, like all the points above, could be a long topic but I’m just gonna keep it simple.

In warm water pretty much any BCD will do. Jacket, wing or backplate with no real consideration than to what you prefer.

However, in cold water the same applies but you now have to take into account your bcd or wing’s lift capacity. With as much as 50lbs/22kgs you may need to use a different bcd you wear in warm water to accomodate all that lead weight.

As well, things need to be more streamlined and positioned deliberately because you have less mobility and possibly big thick gloves that may make it difficult to reach something you could do with ease and without thinking in the warm.

Plan Your Dive, Dive Your Plan

Like sex or pizza there is never a bad dive! Just be sure that you prepare accordingly and can adapt to unforeseen circumstances with the proper training. So venture out. Explore to your heart’s content. Become experienced in both warm waters and cold waters and then you can go anywhere without anxiety. Be a diver that will be prepared, trained and able to plunge into the depths regardless of what temperature you may be plunging into. And most importantly, have fun out there.

Along your scuba diving journey, you may have noticed that some tanks or cylinders have bright green and yellow markings. These tanks represent enriched air, which means the divers are diving with nitrox, a special blend of gas to enrich your diving experience. However, like everything else in diving, nitrox can be highly effective if used properly, or very dangerous if used incorrectly. Let’s take a look at what nitrox diving is, the pros and cons of diving with it, and why some divers prefer diving with this enriched air!

What is Nitrox or Enriched air?

To start out, we’re already trying to confuse you by having two names for the same thing.

Scuba divers are notoriously lazy, which is why we use highly effective fins to swim with, we aim to breathe easily and lazily to conserve our air, and we also like to shorten every name that we can; submersible pressure gauge S.P.G, buoyancy control device B.C.D and so on, and the same is true with Enriched Air Nitrox.

Read More: SCUBA Acronyms – Useful Terms to Know

The word Nitrox is an abbreviation of Nitrogen and Oxygen. This is a term given to any mixture of gas where the oxygen content is higher than 21%.

When this happens we have enriched the mix with more oxygen, so the full name is Enriched Air Nitrox (EANx).  Since divers are already lazy, and Enriched Air Nitrox is a bit of a mouthful (I’m already annoyed at typing it out so much), we just shorten this term to Nitrox.

To make it easy to identify Nitrox tanks, they will be marked differently from normal air tanks. The most common markings are green and yellow stickers or fabric bands, with the word Nitrox or Enriched Air written on them. Different parts of the world may have other colour systems or markings so check locally.

Why Dive with Nitrox?

In scuba diving it is always the amount of nitrogen in our bodies that dictates how deep and how long we can stay down diving underwater.

The deeper and longer we are down the more nitrogen is absorbed into our bodies. Sometimes, depending on the diver and the dive, you will have enough air in your tank to continue diving, but have reached your maximum nitrogen consumption for the dive. This can be frustrating as now you need to end the dive due to your no-decompression limits (NDL).

Diving with Nitrox, however, reduces the amount of Nitrogen entering the body due to the higher oxygen percentage. This means that your NDLs are extended, and in the same situation as before, you would now be able to continue your dive and have an increased bottom time.

Pros and Cons of Nitrox Diving

So far, Nitrox sounds pretty awesome, reducing nitrogen loading to allow more dives in a day or longer, deeper dives (depending on air supply), but it also has some downsides, so let’s look at the pros and cons of using nitrox.

• *As we know from our training, we should always follow the most conservation no-decompression limits, which means if your buddy is not diving with nitrox, then you would need to still follow their limits.

Enriched Air Nitrox Diving Tables

Just as diving with normal air, Nitrox has its own set of diving tables to calculate your no-stop times.

Due to the reduced consumption of Nitrogen while diving on Nitrox we need to use different tables when planning our dives. Nitrox tables are easy to recognise as they will typically be bright yellow and green in color, compared to the standard recreational dive planner (RDP) tables.

These tables will usually come with NDLs or no-stop times based on 32% and 36% oxygen. These figures are the common nitrox blends.

As you can see from above, using 36% EANx gives you more than double the NDL for an 18 m / 60 ft dive.  Planning the dives is exactly the same, making sure you don’t have too much nitrogen in your body throughout any singular or repetitive dive series.

One limiting factor with some agencies’ dive tables is you can only get them in two or three oxygen percentages such as seen in the table above. This is where using a dive computer has massive advantages.

Nitrox diving is considered a gas mix with any blend higher than 21% oxygen. Dive computers (depending on the model) allows you to set the oxygen percentages from a range of 22% through to 50% with some technical computers allowing you to set it up as high as 100% oxygen. This allows much more flexibility when planning dives and having the best mix for the dive you wish to perform.

Read More: Best Diving Computers for Beginners

Dangers of Diving with Nitrox (Why do you need a Nitrox Certification?)

Just as with any diving, using Nitrox comes with its own set of dangers with the main one being Oxygen Toxicity.

Oxygen Toxicity happens when a diver exceeds the maximum partial pressure of oxygen in a gas mix. The deeper we dive, the higher the partial pressure of oxygen becomes. On-land we are able to breathe 100% oxygen safely with no problems, however, at depth this is another story. Because nitrox has a higher oxygen content, we reach the partial pressure oxygen limit at shallower depths. This is the main reason why you need nitrox training and a certification to go diving with nitrox.

Oxygen Toxicity symptoms include;

• Coughing
• Chest pain
• Trouble breathing
• Muscle twitching in face and hands
• Dizziness
• Blurred vision
• Nausea.
• Death

Without the nitrox certification it’s highly unlikely that divers would know how to plan what mix to use and what depth to stay above to prevent oxygen toxicity from happening. This is why it is so important to take an Enriched Air Nitrox course before diving and breathing from a nitrox tank.

Scuba Diving Nitrox Certification

The main part of the nitrox diving course is teaching people how to avoid oxygen toxicity, through good planning and understanding of limits imposed by the gas mixture in your tank.

So, what’s involved with a Nitrox certification?

Theory

• During this part of the course you will learn all the science behind partial pressures and maximum operating depths, how to use Nitrox safely and what to do in emergencies. You will also have knowledge reviews and an exam to complete during this section.

Tank Marking

• While diving on Nitrox certain information is written on the tanks. You need to write the name of the person using the tank, date the tank was analyzed, oxygen percentage and max operating depth. This is done so important details can be found quickly if any problems occur.

Analyzing Tank

• This is completed pre-dive to make sure the gas in the tank is what you asked for. The process is completed by calibrating an oxygen analyser using a normal air tank of 21% oxygen, then the analyzer is used on the Nitrox tank to record the exact oxygen percentage in the tank.

Dive Computer

• If using a dive computer during your Nitrox course your instructor will show you how to set your computer for the Oxygen percentage you will be diving with. They may do a simulation with you, so you can set your own computer on future Nitrox dives.

This is based around the PADI Enriched Air Diver course. Other agencies will have similar courses and structures but may differ slightly. Contact your local dive centre for more information.

Calculating your PPO²

PPO² stands for Partial Pressure of Oxygen. You will sometimes see this written PO².

When diving on Nitrox we are mostly concerned with the pressure being exerted on the oxygen part of the mix, hence, the partial pressure. We calculate the concentration of oxygen that is absorbed at various depths when using Nitrox to remain safe.  

To calculate the partial pressure of O², you multiply the percentage of oxygen by the amount of pressure you are under at depth.

Remember, on the surface we are under 1 Bar/1 ATA of pressure and for every 10 meters of depth we enter a new Bar/ATA of pressure. 

So for example if we were using a Nitrox tank with 25% Oxygen and diving to 20 meters (65 ft). We would do the following calculation: 0.25% O² x 3 bar/ATA = 0.75 PO²

In recreational diving, the maximum partial pressure should be 1.6. Though we plan all dives with a contingency limit of 1.4. This gives us a small buffer in case we accidentally exceed our maximum operating depth before Oxygen Toxicity kicks in.

Here is a table showing Partial Pressures for the most common Nitrox / Enriched Air Blends.

As you can see from the table, without allowing the partial pressure to exceed 1.4 or normal air (21%) we can dive to a depth of around 56 meters.

However, when using a Nitrox mix of 36% we are limited to about 28 meters. These depths are known as the maximum operating depths (MOD).

This is where you need to be highly mindful of your depth when using nitrox. As an Advanced Open Water Diver you would be certified to go to 30 meters, but using EANx36 you can only go to to a depth of 28m safely.

Using a computer makes this much easier. Once you input your gas mixture and the maximum partial pressure you want to follow, the computer will calculate your MOD and some computers will even give you a warning if you exceed this depth limit. Though you should not just rely on the computer’s safety feature; good buoyancy and checking your depth regularly is always the best option to stay safe.

This is also why Nitrox tanks are clearly marked with bright yellow and green bands, so you don’t accidentally use an enriched mix and dive too deep exceeding the safe partial pressure.

How Deep Can You Scuba Dive with Nitrox?

Looking at the above table, the depth you can dive to is going to be greatly affected by the mixture in your tank.

The less oxygen you have in the tank means the deeper you can go, so technically the lowest amount of oxygen in an Nitrox tank would be 22% bringing your max depth to around 53 m / 173 ft.

The maximum depth of recreational diving is 40 m / 130 ft, so unless further technical training is acquired the deepest you can go on Nitrox is 40 meters.  

Can You Dive Longer with Nitrox?

This is a very common misconception with Nitrox!

Sadly, Nitrox is not a wonder drug that gives us infinite air while diving. As we have read, diving with enriched air does reduce nitrogen loads which means we can go to a deeper depth for longer. However, we are still constrained by air consumption and at some point we all run our tanks down to the point when we have to end the dive safely.

This is the same when diving on Nitrox. Though sometimes, as we are able to stay deeper for longer, this means we use our gas quicker than on normal air dives. But why? I hear you say. This is because we are under more pressure for longer resulting in breathing our tank quicker.

This is the balancing act of diving on nitrox; not staying at a maximum depth for so long that we get short dives, but also being able to stay long enough to have the benefits of the reduced nitrogen load.

Pro Tip: UW Photographers love using enriched air for the longer no-deco times. This allows them additional time at a certain depth to capture the perfect shot. Read our tips on how to become an Underwater Photographer.

Does Nitrox Reduce Narcosis?

As we still have nitrogen content in our tanks while diving on Nitrox, the effects of narcosis are exactly the same as diving on normal air.

Read More: What is Gas Narcosis? 

If you encounter gas narcosis on a Nitrox dive, follow the same steps you would when experiencing narcosis on normal air. Ascend to a shallower depth until the effects wear off. If you still feel uncomfortable then you should end the dive.

Scuba Diving with Enriched Air

Hopefully, you now have a much clearer understanding of Nitrox diving and what enriched air is. As you can see, like with any diving it has its risks but as long as it is used safely and responsibly nitrox can really enrich any dive (see what I did there!).

Nitrox is one of the most common specialties for divers to learn, especially for people planning diving holidays with multiple dives per day. With the reduction of nitrogen load and no need to push NDL limits, it really makes those trips more enjoyable. Some divers use the nitrox scuba diving course as a gateway into technical diving. Whatever the reason, nitrox is a great certification to have and let’s be honest, you just look cooler diving with Nitrox!