SDI Diver News

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



Go back to where it all started –by revisiting your original training site

Think back to when you joined the ranks of divers. That amount of time can widely vary, from last weekend to decades, yes decades ago. However long it’s been, you should never let your dive experience mar every opportunity you can to dive.

Involved in training for many years, I have always gotten a kick out of inviting a new diver along on a dive trip. The discussion would usually go something like: “Doing any diving this weekend?” the newbie diver would ask. “Yes, I’m completing open water training for some new divers. You should join us.” Often, the response I’d receive always brought a smile to my face; sometimes I could not contain the chuckle when I would hear. “No, I did my training dives there. I’ve already seen it”. If I was inviting them to a 6 by 6 pit of 33’ of mud I had dug out to “complete training” I would have understood, but I was inviting them to THE FLORIDA KEYS! My response would usually be “Already seen it? All of it? How did you manage to do that?”

As an industry professional, I reflect back on these encounters and realize now I was the one to blame. I must have not presented the diving opportunity properly. Training Dives? Why in the world did I refer to them as training dives? These were people I was going diving with, not walruses or seals! I guess I had fallen in to the trap of referring to them as I had always heard them called: training dives.

If your Instructor made the same mistake, I suggest you go back and revisit the site where you were originally certified. If it’s been a while since you have been in the water, tag along or shadow a group that may frequent the site. But, this time you will see the site through a new set of eyes: diver’s eyes. You won’t be ignoring your surroundings while waiting for your instructor to give you a command to exhibit your proficiency on a given skill you’ll be there to purely enjoy the dive. Be it a lake, river, or ocean, the site where you first started diving deserves a second visit and another closer look.

Chances are, by the time you exit the water you will smile as you think back at the original dives done at this site. Your apprehension and concerns are natural for any diver entering any unknown. After all, isn’t that part of the adrenaline rush for so many divers? And as you fondly reflect on your first course, you will probably have a desire to explore new ones. Maybe a Solo Diver course that hones your skill set like no other or an Intro to Tech. You will find info on these and much more at or locate your closest local facility. You can also peruse our local courses.

I’m reminded of a Divemaster at a popular diving resort that in briefing his guests would state… “If I interrupt your dive more than you like just give me this signal and I’ll know to back off and give you your space.” The signal required the use of one finger, and it wasn’t a thumb indicating to go upwards. You get the idea!

Most important of all, stay diving, stay wet and please stay safe!

Rigging Stage Bottles… How to carry extra scuba tanks… and why.

Rigging a stage bottle – although not something taught in an SDI openwater class – is nevertheless a basic scuba skill. Certainly, it is one of the first things an instructor will discuss with aspiring tech-divers who almost always carry an extra scuba cylinder (or cylinders) with them on all their underwater outings. However, like so much about dive gear and dive practices, there are several tenable solutions, though none work perfectly for every application. In other words, the correct way to rig a stage bottle depends on exactly how you intend to use it!


To find out which options best suit a particular need, we should start at the beginning by asking, “What exactly DO we mean by a ‘stage bottle’ and what purpose is it intended to serve?”


Technically, a stage bottle is a cylinder containing gas that is going to be “staged,” or stashed, during a set-up or preparatory dive along a predetermined route – such as in a cave passage. At some later date, divers will travel along that route, and the stage bottles will help ensure they have something to breathe! Staged gas allows divers to travel further and swim longer than they would if their excursions were limited to only the gas that they could physically carry with them.  Staging gas is an explorer’s trick, and the gas contained in a stage bottle is sometimes left as a contingency and sometimes as part of the overall gas consumption plan.  Often stage bottles are left behind after the “big” dive and collected on a later clean-up dive.


Now, many divers will find this definition to be disagreeable, but take a deep breath because there are a lot more where that came from! A stage bottle is a general term used to describe a cylinder that is carried by a diver in addition to the primary scuba gear (open or closed circuit). A stage bottle can be a cylinder of decompression gas (for staged deco diving), a cylinder of travel gas to help a diver get from the surface to a depth at which his back gas is suitable to breathe (as in with hypoxic trimix), or an additional cylinder of bottom mix carried by the diver throughout his dive to add a level of security should something go awry with the primary gas supply.


Additionally, a stage bottle can be a cylinder of bottom mix used as the main gas supply with primary cylinders as backup ( a common practice with divers riding Diver Propulsion Vehicles), a bailout open-circuit gas for a CCR (closed-circuit rebreather) diver to have if they have to “come off the loop” (jargon to describe the situation when all bets are off and their CCR is not safe to use), a pony bottle carried by a sport diver to provide emergency gas for an Out Of Air event, or a buddy bottle to allow a self-sufficient diver (SDI Solo Diver for example) to have back-up gas and an abundant gas delivery system when diving independent of their buddy.


Wow! Who knew?
On top of that list of applications – or perhaps because of it – stage bottles come in all sorts of shapes and sizes (the shapes are universal, but sizes and cylinder materials vary). The most common stage bottles used by technical divers are the aluminum 80 cubic foot (11 litre) cylinders and its 40 cubic foot (6 litre) little brother. Some divers – particularly sport divers – use smaller cylinders than these as pony bottles. Similarly, a few divers use larger volume cylinders including steel tanks, but when technical divers speak about stages or deco cylinders, the majority have an aluminum 80 or 40 cubic foot in mind.


Quite simply, these are favorites because of low cost, durability, availability, the volume of gas they carry and their buoyancy characteristics; both the 80 and 40 have a very slight apparent weight in water and both tend to “sit” nicely close to a diver’s body, which is a function of their overall length, diameter and buoyancy.
Common to all forms of stage bottles, regardless of their final application, is that they need to be rigged in a way that allows them to be carried by the user without getting in his way and hampering his progress through the water. In other words, ALL stage bottle rigs have to be streamlined and create the least possibility of snagging line, getting hung up in kelp, digging a trench in the mud or smashing against rocks, boats, wrecks, coral etc. In addition, most divers want their stages rigged so that they have unlimited access to its valve and the regulator first stage that will be attached to it.


Speaking of regulators, a working stage bottle will feature a good quality first stage with an SPG (often on a short hose) and a single second stage on a hose long enough to route comfortably to the user’s mouth with the bottle in position. Depending on actual application, the first stage regulator – especially on CCR bailout bottles – may also have a low-pressure inflator hose attached. (See photo).


Finally, most experienced technical divers want their stages configured in a way that allows them to be donned and doffed quickly and without fuss.
With this in mind, by far the most functional rig for the majority of technical divers is one that attaches the stage to the diver’s side and close to his body using a couple of bolt snaps. This is vastly preferred to attaching stages to backmounted primary cylinders; although, one can still see old-school divers with the cylinder containing their decompression gas shoehorned between their doubles behind their back and well out of reach. This backmounted option is also popular among sport divers who sometimes attach a pony bottle to their single primary cylinder with proprietary hardware. On the plus side, it does keep things out of the way; on the negative side, it does keep things out of the way. In other words, out of reach and out of visual contact, when rigged like this, offers no way to manipulate the valve or do a visual check without taking everything off.


So, we find ourselves with an aluminum 80 (or a 40) and a regulator setup just the way we want it. (See photo). Now we need to put some bolt snaps on it.


Here we have a couple of options:


The traditional tech-diver method (actually known as the traditional North Florida Cave Diving method) is to tie two bolt snaps to a length of string, slip that string onto the neck of the stage bottle and attach the bottom end using a stainless steel pipe clamp.  This method is so ubiquitous that various scuba gear manufacturers sell “stage bottle kits” containing all the necessary hardware.  At the time of my last check, this past Saturday, my local dive shop carried pre-made stage bottle kits from three different main-stream technical diving brands. (See photo).


These kits make life simple and since none come with instructions, they must be easy to fit, correct? Well, not exactly. One small refinement often left out of the plan is to “optimize” the location of the lower anchor point so that it fits the diver. This helps to make clipping and unclipping the bottom bolt snap easier and will help to keep the bottle as close as possible to the diver’s body, especially the neck of the bottle.


The trick is to adjust the distance from the clip at the neck of the stage bottle and the lower anchor point so it’s the same as the distance between the Dring on the diver’s shoulder harness and the one on his hip. Since most of the ready-made kits available seem to be made to fit someone about 185 cm tall (about six feet), this exercise usually requires shortening the pre-made string “handle.” (By the way, NEVER carry a stage bottle by its handle; you should carry it strictly at its valve. The handle is for moving bottles around in the water. Carrying a stage incorrectly will stretch the cord and could break it).


A growing trend among both open-circuit and CCR divers is to rig their additional cylinders as sidemount stages. Sidemount rigging requires an additional piece of equipment – a butt plate – and a strategically placed, moderately stout bungee cord. The butt plate is what the lower bolt snaps clip to and the bungee is what keeps the neck of the bottle pulled into the diver’s side. The top clip is simply a backup should the bungee give away. (See photo).


To make the best of this method, the stage can be rigged with a small clip attached directly to the neck of the cylinder with a few turns of the cord and a lower clip (also on a small loop of bungee cord) attached with a pipe clamp. Just as with traditional rigging, the position on the lower anchor point affects the final resting point of the stage, and the aim is to have the cylinder sitting parallel to the diver’s side with its neck – and the regulator – tucked into the area under his arm.


Once again, there are refinements that are made to the lower anchor point when two or more cylinders are to be carried – essentially moving the anchor point closer to the cylinder neck – but the basic starting point on an aluminum 80 is to have the anchor a little less than halfway between the tank’s shoulder and base.


One final point worth mentioning is that all the preferred methods of rigging a stage bottle, whether it is the traditional cave configuration or a more streamlined sidemount method, allow the clips to be cut off in an emergency. In other words, there are no metal-to-metal connections. Bolt snaps, even high-quality stainless steel clips, have the potential to lock shut. This is especially true in salt-water use, but I have had clips that have only seen freshwater diving “freeze” shut.
Being able to cut oneself free of a stage bottle (or camera) beats the alternative in my opinion, and this informs the best practice of attaching clips with something that a decent cutting device can make short work of.


The secret to the effective and efficient control of a stage bottle is thoughtful rigging and practice. If a diver starts out knowing what the stage bottle is to be used for – for example, whether it will only be used as a contingency or whether the gas it contains is an important part of every dive plan – and if that diver follows a couple of simple guidelines, carrying an additional bottle becomes second nature. After some practice, even carrying two or three will be quite easy. Clearing out staged gas after a dive, I have swum with as many as seven stage bottles, at which point there are some other little tricks that help, but the first step is always to rig each bottle in a standard and sensible way.


Good luck, dive safe, and if you are trying to swim with a stage bottle for the first time, practice in shallow water!


While we all have that “special place” we must see, do not miss out on what we have close to home!
Years ago, I recall hanging out around the set of a TV station for an interview about diving. Teaching a local college diving program for many years had brought me the distinction of being somewhat of a “diving expert,” a nomenclature that I will always scoff at!


On the way to the interview, I thought of the places I’ve had the good fortune to dive and those I still would like to visit. I had it nailed in my mind. “Ask away; I’m ready!” I reflected. I sunk into the well-worn couch and waited for the first question.


I heard nothing but a murmur during the introduction process as I continued to rehearse my answer to the inevitable question, “What is your favorite place to dive?” Without a second thought  I blurted out, ”Locally, right here at home!” I certainly didn’t rehearse that!


Despite my quick response, I still stand by my statement to this day. There really is no diving like local diving. Local diving gives you unequaled access and in most cases great variety if you are creative in your approach. Now you may be thinking, “but there’s only one dive site near me!” To this response, I ask: Have you ever seen it through the eyes of other divers? I can assure you the dive you make each time will be as unique as your dive partner if you simply insist they take the lead and ask them to point out anything they see of interest.


Local diving sites can offer many challenges and rewarding moments. They’re a great place to socialize, meet more divers to add to your contact list and a better place to try new gear or acquired techniques.


Here are a few suggestions to stir some interest in your local diving:


  • Get the word out– A simple posting in the Dive Center, Divers blast e-mail, newsletter or social sites will work nicely.  Set up a meeting- Don’t be scared. This isn’t meant to be a serious work meeting; it will be fun! Talk about local diving opportunities and places that someone in the group “has always wanted to check out.”
  • Create a social gathering surrounding the dive– We all know that in the scheme of things a two- dive day does not require a lot of time. But having a barbeque, volleyball match or round of drinks will fill the day nicely.
  • Set a date– Select a time each month to get together, dive, grab a coffee, see a movie or go bowling. After all, you share an important common bond: you are divers!

Remember, everyone’s definition of local diving will vary. One particular group of local divers invited me to one of their monthly rituals. Early on a weekend morning we met at the Dive Center, the regulars retrieving their coffee mugs that proudly hung on the wall. We grabbed a coffee and a donut and marched into the classroom, a destination they had selected last time they met a month ago. We arranged who was driving with whom, consolidated gear and headed out the door.

Any place that could be dived and return home in one day was considered local, but the adventures often spanned a full day. As we headed out the door, the group split, some heading to the 2/3 of a day option while I jumped in with the “let’s go for it all day!” crowd.

By the time we returned to the rendezvous point that night at the Dive Center, it had been long closed and we meandered to our vehicles. As I wearily pulled away, I was approached and asked, “Hey, want to join us for a cold one?” Their day was not over yet, but I was too tuckered out to continue.

You see, local diving is where the fun and friends are! You meet new ones to go explore and answer the ever-burning question: “Hey, I wonder what is at the bottom of …?”
So, what are you waiting for? Start diving locally! Make it happen & make it safe!

To Snorkel or Not to Snorkel: That is the Question


How did this become such a point of contention for so many?
A long debated issue amongst divers, instructors and training agencies is: do divers need to wear snorkels? Before we explore this topic, a little bit of history is in order.


In the beginning, snorkels were a very useful and important piece of equipment. In the early days of SCUBA training, free diving or snorkeling was a big component of the course, acting as an air management tool. Divers were taught to hold their breath and dive down to depths so instructors could assess their comfort in the water.


In addition to cylinder volumes being less, given that SPG’s were not a part of the regulator, the diver only knew the tank was full because the person that filled it said it was. Towards the end of the dive when the “J” valve stopped delivering air and the diver pulled the shepherds hook to get the reserve amount of air to get them to the surface, it was quite possible that the surface swim would have to be performed on the snorkel.


Fast forward to present day: we now have SPG’s, air integrated dive computers, snorkeling skills are not as big of a part of training, and our training materials teach better air management practices. Also, today more divers are going into overhead environments and diving in areas where snorkels become a liability and not an asset. So this brings us to the question: snorkel or no snorkel?


There are still dive sites that require a surface swim, and a snorkel will conserve the air in the cylinder for the dive. There are also locations where snorkels are required by law. In these situations, snorkels are a must.


Where do snorkels become more of a liability? On high current dives, snorkels create a drag and tend to cause the mask to flood. In overhead environments, such as wrecks, swim troughs and caverns, they can cause the divers mask to be dislodged and cause a leak or flood. When diving around kelp or areas where monofilament line is known to be, snorkels become an entanglement hazard.


Another deciding factor is the comfort level of the diver; are you comfortable wearing a snorkel or not? One thing a snorkel should never replace is proper planning of air supply. Divers should always surface with enough air left to make a surface swim to their exit point, be it a boat or shore.


By breathing off the second stage, the diver avoids the possibility of breathing in water that has entered the snorkel due to choppy surface conditions, waves or poorly aligned snorkel (snorkel leaning too far backward or forward). A variety of pocket snorkels have also entered diving, allowing the diver to “always have one with them” although not necessarily attached until it is needed. With all these details, it’s easy to see wearing a snorkel or not depends on the type of dive that is planned.

There is possibly no better exercise and opportunity to interact with sea life than going out for a swim across the surface of the ocean, lake or river. In this case, a snorkel is exactly the right tool for the job. With the brightest sun light, it attracts the highest concentration of life. Find a good fitting snorkel, mask and fins, and the experience is sure to be amazing!

Underwater Journal

Underwater Journal


Underwater Journal

Did you know… the UWJ is the official publication of SDI™/TDI™/ERDI™, a diving certification agency, and is included in the National Oceanic and Atmospheric Administration’s (NOAA) Information Exchange for Marine Educators Archive of Journals?

Did you know … that issue 20 of the UWJ is ready for download?
Here is what one of our readers had to say:
“Many scuba magazines are
about ads and superficial topics. ‘UWJ’ gives me details that
I can’t find elsewhere and
covers all aspects of my favorite
activities in great depth.”
– Vance A. Barr, Glenville, NY
You’re really going to enjoy issue 20. We’ve included some compelling tales of dive destinations both near and far. Doug Ebersole tells of the wonders that can be found just off the coast of Vancouver at a site called God’s Pocket; Tim Rock takes us to Guam to visit marine preserves, and a team of French adventurers travels to Iceland to report on a unique thermal vent found in the relatively shallow depths of a northern Fjord.

History buffs
and wreck divers will enjoy the vicarious discovery of a World war II British fighter in Greek waters, and will be pleased to learn that the easily-accessible wreck of the USS Massachusetts awaits in shallow waters just off Pensacola, Florida. And, as always, we’ve added a mix of product reviews, dive medicine and ocean science to round out the issue.
Stay tuned! We’ve created our first-ever underwater video contest. Slated to run from June 1 to June 30, the contest will give UWJ subscribers the chance to showcase their video, and anyone can vote on favorite entries. All the details will soon be posted on the website.

Whatever your adventure is this summer, we encourage you to share it with fellow divers and with us,. Whether you’re capturing the underwater scene on video for the chance at a great prize, simply posting us a note, or sharing a photo.
Next issue is due out June 15.
PS – Don’t forget, UWJ is iPad compatible.


Headaches and SCUBA Diving

Diving headaches have spoiled many dive trips. As there are different causes associated with headaches and diving, it can be as simple as a mask squeeze, an excessive constriction around the neck by thermal protection, a dental issue, cold water around an inadequately insulated head, or saltwater aspiration.


SDI vs TDI Nitrox: Which One and Why

We are often asked why we have two nitrox programs, one under SDI and one under TDI, and why should someone choose to teach one course over the other…. or even consider both?