3 Reasons Your Mask Leaks

by Cris Merz:

sdi diver

photo by: Santiago Estrada

Mask leaks can certainly make a dive uncomfortable as well as frustrating. Did you know that having a leaky mask is also a contributor to poor air consumption? Aside from the harder breathing that is required due to increased stress, air is constantly blown into the mask in order to blow out the water to clear the mask. Three topics will be covered that may assist a diver with mask leakage issues: hair, mask size, and mask quality. Being aware of how these three factors can contribute to mask leakage may decrease the issues underwater caused by a mask leaking, making for a much more pleasant experience.

#1 Your hair can cause your mask to leak

Hair is a culprit that affects mask leakage that often goes ignored. For both men and women, it is important to ensure that hair is pulled back away from the forehead so it does not interfere with the seal created by the skirt of the mask and the skin. Additionally, men must also be aware that facial hair may prevent the seal from being tight between the upper lip and the bottom of the nose. If shaving is not an option, one may try applying a dab of petroleum jelly or similar lubricant to act as a sealant, though it is not a guarantee either.

#2 Your mask may be too big or small

The size of the mask is usually one of the biggest factors to cause a leaky mask. Some divers believe that a tight strap around the back of the head is the best “fix” for this situation. It is not. A mask that doesn’t fit is a mask that doesn’t fit. Pulling it tighter may just cause further discomfort as well as stress. A mask that does not properly fit may leak with the most minimal movement or even facial expression regardless of how tight the mask strap may be. It is important that when fitting for a mask, the diver finds a mask that is not only their size, but fits the shape of their face. The best way to test this before getting in the water is by putting the mask on the face and inhaling gently without pulling the strap on to the back of the head. The suction should hold the mask in place to the face indicating that the seal is intact.

#3 Don’t skimp on mask quality

Quality of a mask, as well as other gear and equipment, is what can potentially make a huge difference in the quality of our dives. A cheap mask is likely to have a cheap skirt around the frame. High quality silicone will be a lot more flexible and adjust to the curves of the face better than say, rubber. It will also be a lot softer preventing discomfort that may cause unwanted facial movements underwater. Divers unfortunately sometimes go for something cheaper failing to realize the importance of a good mask and what it brings to the table as far as diving comfort.

Removing hair from under the skirt, a proper fitting mask and a good quality product will go a long way to improve air consumption and assist in leaky masks issues. Although following all these tips will enhance the dives it is important to note that the job to ensure little mask leakage is not complete. Once the mask has been selected and hair removed, it is important to make the final adjustments once the diver enters the water. First, ensure the mask is centered on the face. It may also help to pull the mask a bit allowing some air to enter before pushing the mask against the face to push that excess air back out creating a tighter seal. Finally, check the back strap’s position to ensure it is not too high or not too low. Once we start our descent, equalize to your comfort level and you are good to go.

3 Conversation Starters Among Scuba Divers

by Cris Merz:
##Conversation starters among any group usually includes three categories of people; those who genuinely want to know more, those who are being polite and are making some small talk, and those who are looking to inject their own twist or expertise in the matter and “one-up” you. “How many dives do you have? I have a billion…” Diving as a community certainly has its fair share of the latter. We will, for arguments sake, ignore those people in this article and focus on the fun, the education, and what makes for good fun conversation over a cold beverage after a day of diving.

  • Equipment. It is always fun walking around a dive deck looking at other people’s gear. “Whoa! What is that? What does it do?” It is a great way to view diver’s choices of what works for them and why. You learn firsthand from a consumer who may either be happy, or not so satisfied, with the product and the “why” behind it. I once actually saw a man with two rearview mirrors attached to his mask so he would not miss any whale shark sightings. This was in Galapagos where most of the marine life is present due to several strong currents such as the Humboldt Current. On the inflatable heading out to the dive site, we learned that he was an eBay fanatic and that was where he found these interesting accessories that clipped on to his mask. Did it work? Well, in 2 knot current, those babies went flying off the moment he turned his head into the current. It was a great idea though!
  • Travel. I have always loved to hear stories of travel experiences. Far beyond just the dive sites, I have wanted to know how the taxis were coming from the airport to the resort or the boat. What was the boat like? The crew? The food? These conversations about the occurrences top-side are often more interesting than some of the diving, although I definitely want to know about that too. “Dude, they picked us up in this 60’s minivan and we had to weave through Vespas, mopeds, and bicycles that often carried 7 people or more – I’m talking whole families.” “The food was awful… way too spicy”. “The food was amazing… so spicy.” But more than anything, I like to hear about the people they met and the new culture they just experienced and their thoughts.
  • Experience. Far beyond the certification ratings a diver may have, the amount of dives some people have accumulated say a lot. We encourage people to take classes and continue to dive in those areas that interest them. Photography? Perhaps wreck diving? These are the types of fields where a diver may take one or two additional courses and then progress as divers in those fields by diving. Diving, diving, and diving. Looking at sunlight a certain way or the approach toward a certain marine creature while trying to get that fantastic picture is not something you will learn overnight. As a wreck diver, experience and control is what will give you the calm and collective head to figure out what you are doing if something deviates from the original plan. For the most part, people love hearing about these experiences, how you handled yourself and how you prevailed. “Wow…I would have been freaking out if I was surrounded by all those tiger sharks after I exited the wreck. And they didn’t do anything to you? What did you do? Do you have any pictures?”

I have found that though I may have used these conversation starters often, my favorite part was often comparing notes. I am often able to bring something back to the conversation but what I enjoy the most, especially if the person is a great story teller, is listening.

3 Tips for Diving Nitrox Safely

by Cris Merz:
##Diving with Nitrox has brought divers many benefits over the years including longer bottom times, shorter surface intervals, longer repetitive dives, and much more. However, with the good, comes the bad… often followed by the ugly. Nitrox has depth limitations because it increases the risk of oxygen toxicity, among other issues. It is a common misconception that Nitrox benefits deep divers during the dive.

The best way to prepare and plan is to follow three core tips when diving Nitrox.

  • Analyze
  • Label
  • Set Computer

Once you have gone through these three steps, you can establish your maximum operating depth.

Analyze. Take the initiative and put the responsibility in your own hands. It is up to you, the diver, to confirm the mix you have in your tank. Since each “flavor” of Nitrox has a different MOD, you need to make sure yours is safe at your maximum depth and which partial pressure of oxygen is right for your conditions. Many experienced Nitrox divers use a PO2 of 1.6 in warm, calm water, but back the PO2 down to 1.4 in colder more challenging conditions.

Once your tank has been filled, the blender will either check the mixture in your cylinder for you – we advise you to watch – or have you check the mixture yourself. Either method is acceptable, provided you are satisfied that you have the correct gas mixture in your cylinder: because after all, it’s you that has to breathe it!

Label. To complete the process, mark the cylinder Contents label with date, FO2, MOD, Limiting PO2, dive operation name and the name or initials of the person conducting the analysis. Your signature indicates that you take responsibility for the Nitrox that has been delivered to you, and that you are satisfied that your cylinders have been filled properly.

It is important to analyze every cylinder and label the mix on each cylinder. While repeatedly stating this may seem redundant, we know that most Nitrox diving accidents occur when the diver grabs the wrong cylinder because it was not properly labeled, or fails to analyze the cylinder. You need to know what is in your cylinder prior to diving so that you can adequately plan your dive, set the mix in your dive computer and avoid an accident.

Set computer. Prior to every Nitrox dive, you must check your Nitrox dive computer to be sure that it is properly set for the mixture you are using. It is important to remember that there are two settings that you must take note of; the percentage of oxygen and the maximum PO2 to which you are willing to expose yourself. Remember, some dive computers, and their manuals use the term “FO2” (fraction of oxygen). In other words, 32% oxygen is the same thing as .32 FO2 in these cases.

While different dive computers have different default settings for both the oxygen percentage in the mix and the maximum PO2, most default settings tend to be conservative. In many cases, the default setting for the percentage of oxygen will be 21% while the default setting for PO2 is often 1.4. If you do not check these settings and adjust them to your dive plan you will not be getting the full benefit of the capabilities of your computer and Nitrox.

Excellent! You can now plan your maximum depth and bottom time. If you always remember to analyze, label, and set your dive computer to the settings according to your mix as well as your dive plan, you are good to go. And remember, when diving Nitrox; don’t dive below your MOD.

Amazing Underwater Encounters

amazing underwater encounterThere are many reasons to love scuba diving. Some people just love being in the water, or experiencing the thrill and adventure that diving is. Some find it to be a relaxing escape, but almost everyone agrees that exploring our oceans and coming face-to-face with some of the world’s most interesting marine life imaginable – straight from the depths of the mystifying seas tops the list of scuba diving benefits. Whether it’s a rare species of coral, the elusive frog fish or a massive great white shark, we all have had an amazing underwater encounter. At SDI/TDI/ERDI World Headquarters, we want to know… What was your first AMAZING underwater encounter? Share your first-hand account and pictures/videos with us, and we will publish right here for all to enjoy. Just fill out the form below.


Recent Submissions




1. Sea-Horse giving birth!

Back when I was guiding dives in the Galapagos Marine Reserve, I had an experience that blew my mind! Talk about being at the right place at the most perfect time to witness this wonder of nature in the birth of new life. I was leading my group along the wall of Cousin’s Rock looking for neat things among the black coral. Some of the main attractions were the sea-horses, but I never expected to see one that was about to give birth! Luckily, my video camera recorded the whole thing.
Cris Merz

2. AMAZING encounter (while teaching)

whale shark encounter

The most amazing encounter I experienced while teaching was during the SDI Scuba Discovery course with two participants. The students took to the water quickly and easily during our pool session in the morning but naturally, they were antsy to get in the open water environment to experience diving in the ocean. Little did we all know our open water dives were going to be one of my most memorable experiences in the water! After our first descent, we enjoyed a leisurely dive across a beautiful reef in the Caribbean around 10 metres/30 feet. With limitless visibility in crystal clear water; we saw a green moray eel, a turtle, and an assortment of colorful reef fish but we did not anticipate what was coming next… A massive shadow came over us and we looked up to find an enormous whale shark swimming near the surface! We couldn’t believe our eyes as we remained still in the water, hovering, while watching this incredible creature swim away… To make this experience even better, we were greeted by two manta rays swimming around the boat upon our return! They put on a fantastic show as we conducted our safety stop prior to ascending. Now keep in mind, this was the first diving experience the SDI Scuba Discovery divers experienced and the first time I saw a whale shark! It was an amazing encounter while teaching I will never forget.
– Lauren Kieren


To participate, fill out this form, and tell us about your Amazing Underwater Encounter!

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Open Water Certified, Now What?

There is so much out there with continuing education, sometimes it can be a little bit overwhelming trying to choose what the next steps should be. A lot of it may also depend on the region you live in and what your local dives may entail. The bottom line is… the adventure has just started.

Nitrox – When to Dive It

by Cris Merz:

Nitrox Diver

The fantastic stories about voodoo gas seem to have mellowed out a little in the last 20 years. From, “It’ll kill you” to “You will have soooo much energy after the dive”, it never ceases to amaze how nitrox, as a topic for discussion, has always been a leader in misconceptions.

With many reasons in favor of diving nitrox, the reasons for doing so may hold a little more scientific value today than they did 20 years ago.

Few advances in the realm of diving have had a more profound impact during the past two decades than the widespread availability of Enriched Air Nitrox. And nothing has made the switch from diving air to diving nitrox more straightforward or more enjoyable than nitrox programmable dive computers.

Simply put, nitrox – air with additional oxygen content – allows divers to enjoy longer bottom times (and shorter surface intervals) than their air-breathing dive buddies, while staying within the limits that were stressed in their open water training.

Nitrox makes this possible because it contains reduced levels of nitrogen compared to air and less nitrogen translates into more bottom time! But of course there is a price to pay. Diving nitrox does present risks that are not present while diving air and these risks require divers to take additional steps during their pre-dive planning and then adhere to that dive plan.

The number one reason for diving nitrox is safety. When diving with a greater amount of oxygen (32% or 36%) in the mix, rather than air (21%), you decrease the risk of decompression sickness because you’ve lowered the amount of nitrogen you are breathing in at depth – and as we know, nitrogen is the number one culprit associated with decompression sickness.

When should we dive nitrox? Well, whenever the opportunity presents itself. It may not make a great difference but it certainly will not hurt. Unless you go diving beyond the Maximum Operating Depth (MOD) of the mix in your tank, it is beneficial to you every time, though sometimes those benefits are much greater than others based on your diving profile.

The moments when nitrox will make the greatest difference is when you are doing multiple dives over multiple days and are getting close to some of the no-decompression limits your personal dive computer is telling you about.

As stated, when you dive using nitrox you can take advantage of increasing your maximum allowable bottom time. This happens because the extra oxygen added to your breathing gas when it was filled has displaced nitrogen. Because there is less nitrogen in the mix to be absorbed by your body you can spend longer at depth before you reach the nitrogen limit – which is the decompression limit. Secondly, since you are absorbing less nitrogen on a given dive, your surface intervals can usually be shortened.

Being on a live-aboard, hundreds of miles from home where you are doing 3 to 4 dives a day will allow you to see a huge difference if you can compare yourself to those diving on regular air. You have paid a lot of money to get there and you want to make each and every dive count. You do not want to get back in the water for the fourth dive so you can zip about at 50ft/15 meters just because you have reached your no-deco limits for the day – especially when the schooling hammerheads are hanging out around 70ft/21 meters. That is where you want to be… for as long as possible.

Despite having depth limits to be aware of due to the risk of oxygen toxicity, and perhaps some additional costs for the fills, the benefits of nitrox will play a role in your steps to keeping your dives within safer limits than if you were on air.

If you are not yet nitrox certified, find out more about diving with enriched air from your local SDI or TDI instructor.

You will discover that diving nitrox is not rocket science. The concepts are straightforward and easy to understand. Of course, like most things relating to diving, the subject does have another side and if the science and technology behind the basic concepts of nitrox interest you or if you find yourself wondering how nitrox with higher levels of oxygen than 40 percent would affect your diving, you may want to consider continuing on to Technical Diving International’s (TDI’s) Advanced Nitrox Diver course.

Media Luna Hotel y Resort Looking for an ADVENTURE OFF the beaten path?

Recently, La Media Luna Facilities joined the growing ranks of worldwide facilities integrating into the SDI Family.

SDI’s own National Sales Manager, Cris Merz ( asked Saul Martinez to describe in his own words his unique Dive Resort. Hold on and get your passport ready, what you will read will have you booking your next trip by the time you read what Saul had to say!

We have been working for 36 years, providing and serving recreational and technical divers from Mexico and all over the world. Our services include: sales, rent and diving equipment maintenance, Instructor certified, air and Nitrox service, the best T-shirts and souvenirs from La Media Luna.

Stop waiting and Contact us! We are proudly a 5- Star SDI/TDI Instructor Training Center #1003153

“We are as proud to have you as you are to join us” stated Cris, “but tell us more about this unique site.”

Laguna de La Media Luna, Rio verde, SLP México

The lagoon: La Media Luna is at México´s center, more specifically at the middle zone of San Luis Potosí, between the mountains, at 3300ft above sea level, in the Rioverde valley. La Media Luna is a spring of GEO-Thermal waters with a very comfortable temperature that goes from 79 to 90 Fahrenheit, with a maximum depth of 118ft ideal for snorkeling, swimming, camping and diving all the time. Even at winter when the lagoon reaches it´s maximum temperature of 90F!

Temperature between 79 and 90 Farenheit
What mysteries does it have?

What is the history of the lagoon?



Did the lagoon exist 20,000 years ago? Some researchers believe so…

La Media Luna is an ecosystem that has housed several forms of life during thousands of years; there have been great archeological discoveries including the bones of a mammoth belonging to the Pleistocene fauna. It has been said that La Media Luna was a giant natural trap, in which some animals were caught thousands of years ago, thereby leaving their remains for us to encounter during the last 40 years in several expeditions made by Mr. Juvencio Martínez Flores; the INAH (INSTITUTO NACIONAL DE ANTROPOLOGÍA E HISTORIA) for its acronym in Spanish, granted him the ward of the pieces and its preservation.

Thousands of Tiny Fossils

A pioneer diver in the country with a deep respect to the environment, Mr. Flores has preserved all of the archeological pieces under his ward. Owner and founder of Media Luna Hotel y Resort, all of the findings can be seen at the Mammoth museum, at Media Luna Hotel y Resort at (Carr. Rioverde-San Luis Potosí km. 3 esq. Canal de la media luna, CD. Fernandez, SLP México).

Juvencio Martínez Flores

There is no doubt that after the mammoth era around the year 650 A.C.-before the Spanish conquest-Rioverde was inhabited by the indigenous natives called the Pames, Otomíes and Grupos Chichimecas. The natives, who lived at the shore of the lagoon, left us some evidence of their inhabitance. These vessels were placed in the depths of the lagoon using free diving, arrow heads made form obsidian, figurines, pots, among other things from the Pame culture that have been found inside the lagoon. Thanks to the ceramic that was recovered, we know that this zone was of great value, dating back to 100 years after Christ.


Media Luna characteristics:

• 3300 ft. above sea level

• Temperature between 79 and 90 Fahrenheit

• Max depth of 118ft

• GEO-Thermal waters

• Cristal clear water

• No dangerous animals

• Endemic fish

• Turtles

• Thousands of tiny fossils

• Petrified trees

• Springs water

• No currents

• Pleistocene lagoon

• Prehispanic culture PAME

• Prehispanic culture PAME

Geo-Thermal Waters

Endemic Fish

Petrified Trees



The crystal clear water, the biodiversity and the colorful fauna create a calm, peaceful and beautiful underwater world. This place is one of México´s natural wonders. The amazing contrast that La Media Luna has to offer is in part thanks to its vegetation and waters. During a visit, try to envision all of the wonders and moments this lagoon went through and realize that we are just one being coexisting with this vast underwater world.


Now, it is time for action and to book your next “out of this world” unique adventure….

To do so you can simply contact the SDI/TDI Facility nearest you and simply ask them to book it! They will do so through Scuba Travel International (STI).

Visiting your local SDI/TDI facility will allow you to focus on the preparation for your trip or find the local diving facility near you.

For more information you can contact Saul directly:


Media Luna Hotel y Resort®

5 Star SDI/TDI Instructor Training Center #1003153

Boulevard El Refugio-CD. Fernández-Rioverde #650 Esq. Canal Media Luna CP 79650

CD. Fernández. S.L.P. México.

TEL: 01(487)872.1473 FAX: 01(487)872.8255

To learn more about SDI/TDI and the services that are offered please visit or Contact or call 207-7294201 xt 202