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What is the Difference Between a Cave and a Cavern?

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DTS Contributor

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Cave. Cavern. Same. Same. Well in a way that is true. We all use the terms ‘cave’ and ‘cavern’ interchangeably. This blurs the differences between the two. You might use the term cavern incorrectly in a conversation. The only person calling you out on your error is your Geologist friend. Without writing a thesis in geology, let’s look at the definitions and origins of these terms and then bring the question ‘What is the difference between a cave and a cavern’ within the context of scuba diving.

What is the Difference Between a Cave and a Cavern?

The definition of a cave is officially defined as any hollow in the earth. Caves can be naturally occurring or man-made, with horizontal or vertical openings into a rock formation. Furthermore, some portion of the cavity needs to be void of direct sunlight.

In contrast, caverns are naturally formed in soluble rock and have the ability to grow stalagmites and form speleothems. Caverns are often a system of chambers. All Caverns are caves, whereas not all caves are caverns.

So, not as clear a difference as I thought either.

Yet all the time we hear these two terms defining a huge difference in scuba diving. Cave Diving is immediately perceived as hardcore and one of the deadliest recreational activities on the planet. Whereas Cavern Diving is offered as a specialty course by PADI and easily obtainable by any Advanced Open Water certified diver over the age of 18.

Cave Diving

Most recreational scuba diving relies on redundancy and direct access to the surface. A newly certified diver can dive independently as long as they have a buddy. If they lose their buddy, they both ascend directly to the surface keeping to maximum ascent rates.

A procedure like this is not possible if you are penetrating a cave system on your dive. Any problem is exemplified by the fact that you need to first find your way back out and then access the surface near the entrance / exit.

Large recreational training bodies such as PADI do not offer full cave certifications due to the high risk and often very localised knowledge needed to penetrate a cave safely.

TDI (Technical Diving International) on the other hand offers full cave courses.

Learn about the different types of scuba certifications

Therefore ‘cave diving’ is the practice of penetrating an underwater passage beyond the natural light zone. These dives sometimes require the passing of underwater restrictions that require gear removal. Cave divers use lines as references during these dives. Most cave divers rely on their own gas plan and do not rely on a buddy for backup gas. They are independent and conduct the dive as a group, but are responsible for their own safety.

Cavern Diving

A ‘cavern’ in diving is a flooded hollow with a restricted entrance. Often these are entrances to a larger cave system beyond them. The golden rule is the light penetration zone. Cavern divers always remain within the natural light zone with direct access to the exit/surface. Some cavern diving courses include a maximum allowed distance from the exit to atmospheric air, keeping divers safe.

Cavern diving courses are often an introduction to cave diving. Cavern divers still rely on their buddies in emergency situations. It is still a good idea to follow the general rules of what divers should do for their own safety.

To get a feeling for how demanding and potentially deadly cave diving can be, I can highly recommend the documentary film Diving Into The Unknown, which tells the story of a group of cave diving friends from Finland.

Watch the trailer below.

There you have it. When asking ‘What is the difference between a cave and a cavern’ we really need to consider the context this question is asked in. There is a geological difference that has little effect in scuba diving. However, this classification in the diving world between a cave and a cavern makes a massive difference.

Always dive within your training and limits. The Last Dive is a fantastic book that tells the tragic tale of a father and son team of divers that pushed their training limits too far.

Predictions for Scuba Diving after COVID-19

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Emma Ong - PADI MSDT

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Predictions for Scuba Diving after COVID-19

As a person who relies on the scuba diving and tourism industries, for income, and as a career, it may be time to worry. Right now we are in the midst of very uneasy and unpredictable times. However, we can speculate what may happen in the future within the recreational scuba diving industry. Here is what I think about diving after COVID-19:

Overseas Tourism After COVID-19

Travel restrictions will continue for the next few months. Some countries such as Australia and New Zealand are strongly suggesting to their citizens to not travel until at least the new year. This will wipe out a large percentage of tourism that relies on these tourists. Indonesia is a top destination for Australians, with Bali being so close and accessible so tourism numbers there will struggle.

Fiji, another top destination for Australians, and other island nations will also see the ramifications of COVID-19. When travel restrictions are lifted again, these smaller destinations will still see a lack of tourism numbers. This is because they do not have the infrastructure or hospital care to deal with a sickness such as COVID-19. This will deter many tourists from visiting.

Local Tourism After COVID-19

There is a large push to ‘stay at home’ and to spend your money in your local economy. Governments will want you to keep the money local and will incentivize and encourage local travel destinations. With oil and fuel prices down, families and groups will be traveling within their own countries by car. This could positively affect local dive centers.

Local Dive Centers

Local dive shops will offer great services and deals to keep your scuba diving spending ‘in-house.’ They will offer equipment prices with extras such as free or cheaper servicing. This is also a great way to support your local dive shop. Local dive shops may also find a boost in their sales. With more people looking towards purchasing their own equipment instead of using rental dive equipment. There is always a small risk of viral transmission when using rental gear; the mask, mouthpieces on the regulator, or snorkel. We may see more ‘holiday divers’ wanting their own equipment for their own peace of mind.

Learn how to clean your dive gear efficiently to protect yourself from viruses.

Holiday Dive Centers

Dive centers or shops that rely on tourist numbers will struggle. There will continue being a major drop in tourists which means there is less work to go around. Many dive destinations rely on ‘high seasons’ to cover their ‘low seasons.’ Unfortunately, there will be no high season this year. This means dive centers will be highly competitive against each other. This may see a drop in prices (good for the consumer but bad for the dive instructor and the center), which may lead to a drop in service and quality in diving after COVID-19.

Dive Instructors and Dive Masters

Dive centers will close around the world due to a lack of demand. This means there will be less work for dive professionals who rely on that ‘high season’ of work. Experienced professionals will continue working but with less students. And if your pay structure relies on commissions, then you will have less income. New dive professionals will struggle to find work and experience as there simply won’t be enough work to go around.

E-Learning Dive Courses

Already we are seeing large dive agencies pushing for online and electronic learning. This means sending the theory and video components to the student directly. The student will then book their own in-water component with a dive center (local or overseas). RAID (The Rebreather Association of International Divers) and SSI (Scuba Schools International) already had a very good online system for e-learning, and PADI (The Professional Association of Diving Instructors) is just catching up.

Check out the different types of diving certifications available for beginners and professionals.

Dive Skills

Skills such as buddy breathing or buddy checks will be adapted for the current climate. PADI is already looking at ways to adapt specific skills for scuba diving, freediving and first aid courses that require close contact between people. Regardless of what the dive agencies will decide, people will not want to share a regulator on-land or underwater. They will also be hesitant to give rescue breathes in a role-playing scenario.

Collecting Experiences

Despite these perceived negatives for the industry, there will be some positives. This pandemic has changed some people’s thinking and there will be a shift to collect experiences rather than possessions. We may see a rise in recreational diving at some point, when people decide that ‘life is too short’ and are keen to try new experiences such as scuba diving after COVID-19.

Changing Careers

Keen divers who usually only manage to dive once or twice a year may also want to pursue their passion full-time. These people will want to shift their life from a 9-5 office job to a career on a tropical island. We could see a rise in professional courses with more people wanting to complete their Dive Master and Instructor courses.

In conclusion, there are many possibilities for diving after COVID-19 situation has calmed down. We will see a shift from recreational to professional diving courses and more online teaching components. Short-term, we will inevitably continue seeing a fall in tourism numbers. But we may see an eventual rise that could exceed previous numbers. Either way, the best thing is to not panic. And to continue doing the things that you enjoy and are good for your well-being. Which definitely includes scuba diving!

What are your thoughts on the diving and tourism industries after this pandemic? Will there be a shift in where you spend your money, or the career you choose? Let me know in the comments below.

Can You Open Your Eyes in the Ocean?

DTS Contributor

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I feel at home in the ocean. I love to swim in it, scuba dive, and even live near it. Humans, however, are not built for the ocean. If you are curious like me you might be wondering if it is possible to see underwater. Can you open your eyes in the ocean and will it sting?

Can You Open Your Eyes in the Ocean?

The short answer is yes, you can open your eyes in the ocean. Clean ocean water is not harmful to your eyes. The salt stings a little, but this passes very quickly. Some refer to this as ocean water eye irritation.

You are however more prone to water-borne pathogens infecting your eyes. I personally have never had an eye infection and open my eyes in the ocean on a regular basis. This begs the question, is saltwater good for your eyes? Saline, after all, is one of the best treatments for eye infections. The catch is that saline is just water and sodium chloride, which is otherwise known as salt. The ocean has lots of bacteria and other substances in it. These have the potential to be harmful.

Our recommendation is to rinse your eyes after a day of snorkeling or scuba diving. This is how you clear the bacteria from your eyes and prevent them from causing eye infections.

How to Open Your Eyes Underwater?

The first few times you attempt to open your eyes underwater might be difficult. I remember having a reflex against opening them at first. So to start out, I recommend opening them really slowly in confined water. Squinting at first and then opening slowly one eye at a time. This will allow you to get used to it and manage the stinging better.

Can You Open Your Eyes in Chlorine Water

When we are talking about chlorine water, we are talking about swimming pools. Chlorine is used to stop bacteria and algae growth in swimming pools. While prolonged exposure to chlorine water is not great and some people can have a reaction to it, it is generally not harmful to your eyes.

Can You Open Your Eyes in a Saltwater Pool

Saltwater pools actually use a process called electrolysis, which turns salt into chlorine. These pools tend to smell less of chlorine and are generally favored as scuba diving pools since they are less damaging to scuba diving equipment. As for opening your eyes the same applies here.

Opening Eyes Underwater: Can You See Clearly?

Now that you know the answer to can you open your eyes in the ocean, you might be wondering what it looks like? From experience, I can tell you that opening your eyes underwater creates an image that is very blurry and appears brighter.

Consider the image on the left as seen with the naked eye underwater. It is blurry and it is difficult to make out any detail. The image on the right appears sharp and closer to the observer. This is the same scene observed using a mask.

Let’s not get too scientific as to why this happens. Basically a camera lens or our eye is able to focus by refracting light rays. These first pass through air and then through a liquid in our eye that functions as a lens. Light rays when passing from one medium through another change refractive index. This allows our eyes to prefocus an image so that we are able to see clearly in the air. A mask adds a pocket of air allowing our eyes to function in the same way. It does, however, distort the image, making it appear 33% larger and 25% closer.

If we attempt to see underwater with the naked eye, we lose the ability to pre-focus an image since seawater and the liquid in our eyes have virtually the same refractive index. This phenomenon is exemplified by the fact that light is absorbed underwater and our eyes need to widen their pupils in order to let more light in. Wider pupils allow the light rays to enter the eye at greater angles making the image even blurrier.

Michael Holcombe delves into more detail in his write up.

Interestingly there are humans that see more than twice as clearly underwater than the average person. These are known as the Moken people whom primarily inhabit the Andaman sea between Thailand and Myanmar. Moken children have learned to control their pupil dilation in order to focus light rays more closely resulting in clearer underwater vision.

Occasionally you meet Moken people during dive trips in the Mergui archipelago.

Watch more in this BBC segment below.

So there you have it, you can open your eyes in the ocean. The discomfort is temporary and if you rinse your eyes afterward there is very little risk of eye infection. Seeing underwater can help you during scuba diving training when you remove your mask underwater. A blurry picture is better than not seeing anything at all.

Read More: Learn How To Clear Your Mask Underwater

What is a Dive Watch and Dive Computer

EQUIPMENT

DTS Contributor

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A dive watch was and is the epitome of wealth, class, and good taste. It is a watch that is rugged, durable, and looks damn good. But what is a dive watch and how was it used underwater? Here we look at dive watches, and how dive computers have now replaced this item in recreational scuba diving.

What is a Dive Watch

According to The Berner’s Illustrated Professional Dictionary of Horology (horology being the study and measurement of time), a diving watch is a ‘watch designed to withstand immersion to a depth of at least 100 m and to satisfy requirements specified in ISO standard 6425.‘

The ISO’s (the International Organization for Standardization) standard includes having a measuring system to indicate time and duration that needs to be visible in the darkness. In a dive watch, this is the bezel that can be adjusted underwater. It also includes other factors such as shock resistance, salt-spray resistance, anti-magnetic, water resistance, and a condensation test.

An orange faced Doxa Dive Watch — Dive watches need to adhere to strict ISO standards. Photo / Down to Scuba

Diving watches were very popular in the day. It signified wealth, class, and adventure for the wearer. These diving watches were produced under high standards as seen above and by well-known jewelry brands. The dive watches were also used by scuba divers (when diving was a seemingly exclusive sport) along with a depth gauge. By using a time-measuring device and a depth gauge, divers could use the Dive Tables to work out their No Decompression Limits to dive safely.

Read More: What is Decompression Sickness or ‘The Bends?‘

A Doxa Dive Watch side on — This Doxa dive watch has an extended band to accommodate a wetsuit or dry suit. Photo / Down to Scuba

What is a Dive Computer

Nowadays, a dive watch can be referred to and known as a dive computer. This computer can be worn on the wrist like a dive watch. It will have a digital display and at a minimum, it will tell you the following things underwater:

The date
The current time
The water temperature
The current depth
The maximum depth you reached on the dive
The time elapsed so far during the dive
Your No Decompression Limit (NDL) the time you have left at that depth before you absorb too much nitrogen and run the risk of Decompression Sickness (DCS)
The oxygen percentage that you will set yourself (most dive computers will automatically be set to Air 21%, but you can change the percentage if you are diving on Enriched Air (nitrox)

Read More: The Best Dive Computers for Beginners

When reading a dive computer after the dive, your dive watch/computer will tell you the following:

The date of the dive
The time you descended for your dive
The average water temperature
The maximum depth
The duration of the dive
The average depth of the dive
The oxygen percentage from that dive
The surface time that has elapsed since you came up from the dive

Other options in a dive watch/computer can include:

A stopwatch
A graph to show you the depths of your dive
Your No Decompression Limits for your next dive
A digital compass

The difference between a dive watch and a dive computer

Nowadays, a diving watch will be left at home in a safe and secure place while you go for a scuba dive. This is because they are often highly expensive items that are worn on-land, and made to be seen and not actually get wet. Brands that make diving watches include; Rolex, Victorinox, Le Jour, Doxa, and Longines.

Divers, nowadays, want their information to be easily and clearly read underwater. So a digital display that can light up; with NDLs, temperatures, oxygen percentages, and of course, depth, is better than a flashy, solid piece of metal. However, that’s not to say that I would say no to wearing both a dive watch and a dive computer!

Scuba Diving with Soft Contact Lenses

Emma Ong - PADI MSDT

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In my teens, my eyesight was tested and I was found to be short-sighted and needed to wear glasses. This was a catastrophe as it was just not cool. As I got older, I learned how to poke my eye without flinching and transitioned to contact lenses. Much cooler. However, wearing contact lenses came with its own issues.

Sleepovers meant making sure I remembered to take my contact lenses container and solution. Nights out meant I ended up sleeping with my lenses in. This left my eyes dry and red from having them in too long (and probably from a hangover)! And when I started scuba diving I needed to find a way to make sure I had 20/20 vision to see the amazing things underwater. AND also keep my hands and eyes clean when using contact lenses. Along the way I figured some things out so here are my tips for scuba diving with soft contact lenses!

Scuba Diving with Soft Contact Lenses

Firstly, good job with choosing soft contact lenses for your water activities! Soft contact lenses are the better choice for scuba diving. They allow gases to permeate and escape. Whereas hard lenses may cause nitrogen bubbles to get stuck on the lens. The large size of a soft contact lens also helps it remain in place on your eye when coming in contact with water. It is also generally more comfortable to wear.

However, soft contact lenses are designed to absorb moisture. This means that they may absorb salt water when your eye comes in contact with the water. This does mean you need to keep the contact lenses clean and sterile. Which can be a bit difficult if you do not have access to soap for your hands or your contact lenses solution.

Bring Spare Contact Lenses

The biggest tip I give to my students for scuba diving with contact lenses is to always bring spare lenses! It doesn’t matter if you are only going for one dive, take a spare pair with you. The worst thing is jumping in for a dive and losing a contact lens before you even descend. And yes, that has happened to me. At a dive site that was 2.5 hours away from land! But luckily, I had a spare pair on the boat. So while my group waited and remained on the surface, I jumped back onto the boat and put in a new lens. I definitely did not want to go on a dive with poor eye-sight and not see the tiny nudibranchs!

Clean your Hands

This is an important tip too. There is no point in bringing a spare pair of contact lenses if you can’t clean your hands. The biggest risk of wearing contact lenses is infection and bacteria entering your eye. This is usually caused by dirty fingers and hands. If you don’t have access to clean water and soap on the boat, then my tip is to bring hand sanitizer on the boat or shore. Rub your hands with some hand sanitizer and then pour some drinking water over your hands to remove any residue alcohol (this could sting your eye!).

Tell Your Buddy about your Contact Lenses

You don’t want your dive buddy to think you are making advances on them underwater when your eye is irritated and you’re constantly blinking and winking in their direction. Unless you want them to think that.

The best way to avoid their confusion while you’re signaling a problem with your eyeball is to let them know in advance that you are wearing contact lenses. In a worst-case, if your contact lenses are irritating you underwater you may need to close your eyes to avoid the stinging pain. Having a buddy who knows what is going on means they can assist you back up to the surface by holding onto your arm and checking on your air and NDLs.

Keep Your Eyes Closed During Mask Skills

If your eyes are easily irritated by saltwater then you should close your eyes when practicing a mask flooding exercise or when clearing your mask. You can also close your eyes when jumping into the water as some water may enter from the force of the water. There have also been very rare cases when a contact lens can slide out of your eye when flushed with water. Closing your eye helps keep it in place.

Eye Drops during the Surface Interval

It’s a good idea to use lubricating eye drops made specifically for contact lenses before and after the dives. This helps rinse off any residue saltwater from your eye. It also stops your eye from getting dry and irritated.

Check out whether snorkeling with contact lenses is a good idea or not.

Other Options to Contact Lenses

Here are some other options if you are worried about scuba diving with soft contact lenses. You can look into purchasing or renting a prescription mask from your dive center. Just be aware that once you are back on the boat you will need to locate your glasses. It’s a good idea to keep them somewhere handy and easily accessible.

You can also look into purchasing stick on corrective lenses for diving masks. These are inexpensive, reusable, and can fit on any dive mask. Some of the lenses are even magnified to help you read your computer and gauges!