Blogs
Decompression Myths: Part 3
By Mark Powell
In the [first] and [second] articles in this series I covered some myths that may have made you think about things in a slightly different way but on the whole were fairly uncontentious. This article may be a bit more contentious as the subject we are going to discuss is a topic that is regularly taught by some agencies and instructors yet has been shown to be a myth.
When I learnt to dive, I was taught there were three golden rules;
1. Never hold your breath while ascending
2. Never dive alone
3. Never dive deeper than your previous dive.
This was in the late 80s and things have moved on since then then in many ways. Equipment has changed beyond recognition and so have many training practices. SDI was launched in 1998 and just one of many firsts was the launch of a Solo Diver program which has shown the diving industry that it is possible to solo dive if you are properly trained, equipped and have the right mindset. For more detail on how the approach to solo diving has changed take a look at this [https://vimeo.com/49259855].
Equally, the idea that you should never dive deeper than your previous dive (also known as a reverse profile) has also been revisited. If you were taught that you should never dive deeper than your previous dive for safety reason in the last 5, 10 or even 20 years then that information is based on an outdated view. The reason I say up to 20 years is that the ‘revisited’ information is based on the Reverse Profile workshop that was held in 1999. In other words, this information has been available for over 20 years.
The information below is not just my view or the view of an individual training agency. The reverse diving workshop was held at the Smithsonian Institute and was organised by DAN, AAUS, DEMA and Dive Training magazine. In other words, it was a genuine scientific workshop and so its findings should be taken seriously.
These workshops are held regularly and the intention is to review key principles and to see if the scientific recommendations are still valid, or whether they need to be updated based on more recent evidence. They follow the same overall format. First the original evidence that led to the current guidance is reviewed, then any more recent evidence is reviewed and finally a recommendation is made based on the total evidence. In this case they followed the same procedure but when they came to review the evidence upon which the original recommendation was based, they made an interesting discovery. There was no scientific evidence that was originally used to create this golden rule. In tracing the background to this rule, they found the first mention of it was in an agency training manual from 1974. This manual stated that if you do the deeper dive first, and a shallower dive second, then you will get more overall dive time according to the tables. This is absolutely true, almost all tables will give the same result. However, there was no indication at this point that it was for any safety reason. Subsequent iterations of this and other training manuals gradually strengthened this statement until, eventually, it became the absolute rule that “though shall never diver deeper than your previous dive”. However, as the workshop discovered, this was never based on any scientific evidence that this was because reverse profiles were more risky than ‘normal’ profiles.
MYTH: Never dive deeper than your previous dive
Furthermore, the workshop confirmed that since the introduction of this rule there had been no subsequent research that showed an increased risk of DCS with reverse profile diving. This should not really be a surprise as many commercial, scientific and even large numbers of rogue recreational divers have been doing reverse profile dives with no apparent increased risk for many years.
In order to remove any doubt, the findings and conclusions of the workshop are reproduced below in full.
Findings:
- Historically, neither the U.S. Navy nor the commercial sector has prohibited reverse dive profiles.
- Reverse dive profiles are being performed in recreational, scientific, commercial and military diving.
- The prohibition of reverse dive profiles by recreational training organizations cannot be traced to any definite diving experience that indicates an increased risk of DCS.
- No convincing evidence that reverse dive profiles within the no decompression limits lead to a measurable increase in the risk of DCS was presented.
Conclusion:
– We find no reason for the diving communities to prohibit reverse dive profiles for no-decompression dive profiles less than 40 m/130fsw and depth differentials less than 12 m/40fsw.
If you want even more information and want to read the full details of the workshop the final report is available in full [https://repository.si.edu/handle/10088/2724].
From this we can see that there is no evidence for banning reverse profiles based on safety reasons. Of course, there may be other reasons why doing the deeper dive first may be a good idea. We have already discussed that you will get more overall No Stop Time on the tables if you do the deeper dive first. In addition, if you do a deeper dive first and use up some of you gas you can potentially do a shallower second dive while staying within safe gas limits whereas this may not be possible the other way around. Finally for divers that suffer from ear problems sometimes a deeper second dive may cause difficulties with equalisation.
However, the key point is that none of these relate to DCS risk. This is an important point because, if you remember from the first article, I said that one of my intentions is to promote a better understanding of DCS risk. If we are telling divers that there is an increased risk of DCS with reverse profile diving, when the scientific evidence says otherwise, we are reducing understanding of DCS risk rather than increasing them. You might not think this is important but I think if we have a key principle of decompression theory that instructors teach as a fundamental safety rule but science says is not true then divers may also question what other key rules are not true.
Sticking to a rule just because that is what we were first taught when the scientific evidence indicates it is not true just serves to spread misunderstanding and is exactly why myths develop. So next time you hear someone saying it’s safer to do your deepest dive first ask them what evidence they have for that.
Just in case you were wondering; the rule that you should never hold your breath while ascending is still good advice.
Exciting news is on the horizon at the beloved dive resorts, Magic Resorts Philippines!
On January 2nd 2005, the journey of Magic Resorts began, when Magic Island opened its doors as one of the first dedicated dive resorts in Moalboal, Cebu. Now, as we look forward to 2025, a significant milestone is on the horizon: Magic Island’s 20th anniversary!
In preparation for this momentous occasion, the resort has recently upgraded their facilities, including renovated bathrooms, ensuring a fresh and modern experience for their guests. The stage is set for a fantastic celebration!
To cherish and celebrate two decades of incredible diving experiences, Magic Resorts will be offering a special 20% anniversary discount to all guests celebrating with them at either Magic Island or its larger sister resort, Magic Oceans in Anda, Bohol, throughout the entire year of 2025!*
NOT CONVINCED YET?
To kick off the anniversary celebration, here are 20 reasons to book your holiday at Magic Island in 2025!
1) 20-year anniversary!
Of course the anniversary is the perfect occasion to stay at Magic Island and the anniversary special offers you to enjoy a stay with 20% discount! Whether you’re a seasoned diver, new to scuba, a past guest, or a new to Magic’s concept, this is an excellent opportunity to experience the magic of Magic Island Dive Resort.
2) Amazing marine life
Moalboal has been a top dive destination in the Philippines for decades, and for a good reason. This laid-back town at the Westcoast of Cebu offers unforgettable experiences for divers and non-divers alike. Located in the Coral Triangle, Moalboal boasts hundreds of coral species and unique critters, but also features unique sights that make it a standout dive destination not just in the Philippines, but globally!
3) Enjoy newly renovated bathrooms first-hand!
In preparation for the 20-year anniversary, Magic Island renovated all bathrooms of the bungalows last August 2024! The new, spacious and modernized bathrooms offer the best comfort during your stay. As a visitor in 2025, you’ll be among the first to enjoy these upgraded amenities with a perfect view.
4) Dive with Whale Sharks the whole year around
Magic Island offers the possibility to dive with Whale Sharks throughout the entire year!
Unlike many other accommodations that only offer snorkeling with the Whale Sharks, Magic Island is accredited to dive with them with their own dive masters, tanks and crew.
5) Easily accessible house reef
Magic Island’s house reef is open 24/7 and easily accessible within only a few steps from the dive center. You are welcome to make an unguided house reef dive any time of day with your buddy. The house reef starts with a sloping area where you can find the resident sea horse and blue ringed octopus among other life, whereafter you’ll reach the amazing wall where you’ll find turtles, nudibranchs and much more!
6) Native-style bungalows with Western features
The modernized bathrooms are a great Western feature in the native looking style bungalows. While the bungalows have their Filipino native style look, with Nipa rooftops, bamboo balconies and panels of Amakan (woven split-bamboo), they have Western amenities such as air conditioning and a minibar.
7) Dive the Sardine Ball the whole year around
One of the reasons why Moalboal became famous for divers in the first place: you can dive the Sardine Run the whole year around! It’s not a seasonal sighting like other places and therefore a very special phenomenon (even for marine biologists). You can dive with over a million sardines while staying at Magic Island every day of the year!
8) Unparalleled service
The excellent staff of Magic Island ensures you have the best time possible. The team members have been part of the Magic journey for many years – some even from day one! The outstanding Philippine hospitality combined with their experience are the perfect ingredients for exceptional service. They’ll remember your name and do whatever they can to make you feel at home from day one.
9) Fully equipped dive center on site
Magic Island Dive Resort has its own fully equipped PADI dive center right on site. The dive center is equipped with 3 compressors (providing nitrox as well), 3 Bangka boats, full sets of rental gear, aluminium tanks with Int. & DIN connection, and an in-house instructor to name a few. Walk down to the dive center in less than a minute after your meal in the restaurant and get ready for diving!
10) Mating Mandarin fish on the house reef every day!
The real signature dive at Magic Island is without a doubt the Mandarin dive. Just a short swim from the dive center leads you to an underwater spectacle that’s nothing short of magical. Every day during sunset, the Mandarin fish emerge from their coral hideaways for their mating ritual. These colourful and beautifully patterned fish are a species of the Dragonet that are rarely seen outside their coral homes except during this special time. A great sighting just in Magic Islands’ backyard and a great challenge for photographers!
11) Beyond regular night dives
In addition to standard night dives, Magic Island elevates the experience with unique offerings like Fluoro dives and bonfire dives, providing a completely different dimension. If conditions permit, you can also embark on black water dives, where you’ll encounter the mysterious and seldom-seen creatures that emerge during night time.
12) Go down with a local expert!
The dive team of Magic Island make your underwater adventures hassle-free and fun.
You don’t have to carry your tanks or set up your gear, they will take care of that for you. The team of trained PADI Dive masters is local and know the area better than anyone. With their experience, incredible eye for detail and sense of humour, you will have the best dive experience!
13) More than 30 dive sites in less than a 25-minute boat ride
On one of the traditionally Bangka boats, Magic Island takes you out diving around the whole peninsula of Moalboal. 30 different dive sites are waiting for you to explore, all within only a 25-minute. Moalboal’s highlight, Pescador Island, is only 10 minutes away!
14) Freshly prepared meals in family-dinner style
The dining area at Magic Island fosters a sense of community with interconnected tables that encourage socializing. Enjoy a diverse selection of freshly prepared local and Western dishes while watching the chefs at work in the open kitchen. Dietary restrictions? Just let them know, and they’ll accommodate your needs with care.
15) Wet adventures above the surface!
Aside from diving, Magic Island offers great daytrips to explore the culture and nature of Cebu Island. One of the absolute highlights is a trip to the Kawasan Waterfalls, where you can choose between a relaxing visit to enjoy the fresh water and stunning views, or an adventurous canyoneering experience with hiking, climbing, jumping, gliding, and swimming.
16) Experience Moalboal in peace
While Moalboal is a popular destination, Magic Island provides a serene escape from the hustle and bustle. Tucked away from busy areas, the resort creates a tranquil oasis where you can relax while still being close to Moalboal’s vibrant life.
17) Suitable for each kind of diver
With just 10 bungalows, Magic Island offers a cozy and intimate setting for all types of travelers — whether you’re in a group, a couple, or traveling solo. The rich marine life and accessible diving conditions make it an ideal destination for divers of all experience levels.
18) Unique signature drinks!
The homely bar at Magic Island offers a range of beverages to enjoy while taking in breathtaking ocean views. Don’t miss the signature drinks made with Ube Cream, a local liqueur that won the World’s Best Cream Liqueur title at the 2022 World Liqueur Awards. Experience the true Filipino fiesta spirit with this exceptional drink.
19) Combine with Magic Oceans
You can extend your wonderful stay at Magic Island elsewhere! Magic Islands newer and bigger sister Magic Oceans in Anda, Bohol opened its doors in 2015, offering you the possibility to get the maximum out of your magical dive trip by combining the two locations. The same ambience, quality of serviced and most importantly: an amazing diving experience!
20) Just because you’ll have a great time!
The reasons to visit Magic Island in 2025 are endless, but the most important one is that you’re guaranteed to have a fantastic time. With exceptional service, friendly and experienced staff, an ideal location, and outstanding diving, Magic Island promises an unforgettable experience.
CONTACT MAGIC RESORTS FOR YOUR QUOTE ON AN UNPARALLELED DIVING HOLIDAY!
Email: reservations@magicresorts.online
Website: www.magicresorts.online
Facebook: www.facebook.com/magicisland.diveresort
Instagram: www.instagram.com/magic_island_dive_resort
Diving in Gibraltar is an experience that truly sets itself apart. Situated at the confluence of the Atlantic and Mediterranean, it offers an underwater world rich in both marine life and history. Whether you’re a complete novice or a seasoned diver, Gibraltar is ready to take you on an unforgettable journey beneath the waves.
One of the most remarkable aspects of diving in Gibraltar is the artificial reef project. Over the years, several ships have been deliberately sunk to create vibrant underwater habitats. Among the most popular sites are the Spanish Barges, 482M, and Batty’s Barge, all located in the local favourite, Camp Bay. The Spanish Barges are a series of four wrecks, two of which were sunk as part of Gibraltar’s artificial reef programme in the 1980s. They rest at varying depths, ranging from 7 to 22 metres, making them accessible for divers of all skill levels. These wrecks, now teeming with marine life such as octopuses, conger eels, and nudibranchs, offer something for every diver, whether they enjoy swimming through wreckage or observing how marine species have transformed these vessels into thriving ecosystems.
For those more interested in history, Gibraltar’s waters host incredible wrecks like the SS Rosslyn and SS Excellent. The SS Rosslyn, a Cardiff-built steamer, sank in 1916 after dragging its anchor in a storm. Now lying at a depth of 23 metres, this 350-foot wreck attracts advanced divers eager to explore its remnants. Newer wrecks, like the Seahawk, sunk in 2002, and the Sun Swale, sunk in 2015, are part of Gibraltar’s ongoing reef expansion. These more recent additions are rapidly becoming important habitats, drawing species such as cuttlefish, spider crabs, and lobsters. Each of these wrecks offers divers the chance to experience a fusion of history and nature, with the wrecks evolving into vibrant marine environments over time.
Another must-see is the Seven Sisters Marine Conservation Zone (MCZ), known for its rich biodiversity and contribution to the protection of marine species. This area is located close to The Inkwells, where divers can still find remnants of 18th- and 19th-century artifacts, including ceramic pipes, gin bottles, marble fragments, and cod bottles, lending a treasure-hunting aspect to each dive. Exploring this site is like taking a step back in time while being surrounded by a thriving underwater ecosystem.
The diving conditions in Gibraltar are just as diverse as the marine life it hosts. British Gibraltar Territorial Waters is home to a wide array of species, far more life than many other areas in the Mediterranean. This impressive biodiversity is largely due to the nutrient-rich waters that flow where the Atlantic and Mediterranean meet. Divers frequently encounter octopuses—Gibraltar’s charismatic species—along with conger eels, moray eels, thornback rays, and spider crabs. Lucky divers, especially during certain times of the year, might even spot Bluefin Atlantic Tuna swimming through the bay while feeding, as well as many other pelagic species. The sheer abundance of fish and the variety of species make each dive an exciting and unique experience, offering something new with every descent.
Gibraltar boasts its accessibility to diving and a wealth of different dive sites depending on your diving abilities, qualifications and experience. The South and East side dive sites are fantastic boat dives ranging in depths from 14m to 35m + where you can dive on rocky biogenic reefs with a vast array of marine life.
You will need a permit to dive which is easily issued by the Department of the Environment or you can dive with licenced dive operators who will cover this for you. There are also very active local BSAC dive clubs you may wish to get in touch with.
Gibraltar offers a full range of diving experiences for everyone, from first-timers to seasoned veterans. Shore diving is conducted six days a week, and on Sundays, you may venture out on a boat to explore some of the more distant wrecks, such as SS Rosslyn and Sun Swale. What makes diving in Gibraltar so accessible is that all our dive sites are within a 15-minute drive/boat ride, making it easy to fit multiple dives into a single day. Whether you’re taking your first steps into the underwater world with a try dive or you’re an advanced diver looking to explore wrecks and caves, we ensure that each dive is tailored to suit your needs and experience level.
Operations start early, and by 8:45 AM, dive centre teams are already busy preparing for the day’s dives ensuring everything is in place for divers. A typical dive day begins with a briefing that covers the dive plan, safety procedures, and site management, ensuring that everyone is comfortable and prepared for the adventure ahead. Whether it’s exploring historic wrecks or spotting charismatic marine life, each dive offers something special. After the first dive, you surface, switch tanks, and enjoy a surface interval sharing stories of what has been seen before briefing up for a second dip!
In addition to providing unforgettable diving experiences, Gibraltar is deeply committed to marine conservation and scientific research working closely with the Department of the Environment and the University of Gibraltar. Under the water we facilitate the university’s research on projects including coral health assessments and the transplantation of coral species such as Astroides calycularis and various gorgonians. These efforts are critical in preserving Gibraltar’s underwater ecosystems and ensuring that future generations of divers can enjoy its incredible biodiversity. These conservation initiatives are ongoing, and there is regular collaboration with students and researchers on various dive-related projects as they begin the Thesis modules of their degrees.
Dive Charters, Gibraltar’s predominant dive centre is also involved in some octopus research, with a project aimed at increasing the octopus population in Gibraltar’s waters. Working with the University of Gibraltar and the Department of the Environment, they have installed artisanal dens designed to encourage octopus to breed and thrive in the area. These dens have proven highly successful, and divers often encounter octopuses up close in their natural habitat. Observing these intelligent, curious creatures in action is always a highlight of our dives, and their growing population is a testament to the ongoing conservation work.
Diving in Gibraltar offers an unparalleled blend of history, marine life, and conservation. Whether you’re captivated by centuries-old shipwrecks or amazed by the diversity of species that call these waters home, Gibraltar provides a diving experience like no other and we are proud to share this incredible underwater world with divers from all over the globe. Our dedication to safety, fun, and environmental responsibility ensures that each dive leaves a lasting impression.
From beginners to experienced divers, we’ve got something for everyone. With all dive sites just a short ride away the wonders of Gibraltar are waiting for you!
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