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than your previous dive for safety reason in the last 5, 10 or even 20 years then that information is based on an outdated view.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.
Blogs
Dive into Adventure at Hideaway Beach Resort & Spa: The Ultimate Diving Destination in the Maldives
Tucked away in the remote northern Haa Alifu Atoll, Hideaway Beach Resort & Spa is a premier destination for anyone seeking an unforgettable underwater experience. With over 30 dive sites to explore, divers of all levels can witness the unique and mesmerising beauty of the underwater world. Whether you’re a seasoned diver or new to the sport, Hideaway offers an exceptional diving adventure that is not to be missed.
Explore the Beauty Beneath the Surface
Hideaway is perfectly situated near some of the most spectacular dive sites in the Maldives. The dive school and team at Hideaway offer a very personalised experience to ensure each diver gets an interactive, immersive experience.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Unique dive spots such as Theefaridhoo Thila (Heaven and Hell) as one of the 50 best dive sites in the whole of the Maldives, known for its beautiful soft coral gardens.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
As the resort is located next to a channel which gives guests surprise visits from eagle rays, manta rays, guitar sharks and more.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
One of the standout features of diving in the Haa Alifu Atoll is the abundance of rare and exotic marine species. The area is known for sightings of whale sharks, manta rays, turtles, and a variety of colorful reef fish. Diving at Hideaway Beach Resort & Spa offers a rare opportunity to encounter these creatures in their natural habitat, creating lifelong memories for guests.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Whether you’re exploring deep coral gardens, dramatic overhangs, or vibrant reef walls, each dive offers something new and exciting. The visibility in the Maldives is exceptional, often exceeding 30 meters, making it ideal for both underwater photography and general exploration.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Diving for All Levels
At Hideaway, we believe that everyone should have the opportunity to experience the thrill of diving. That’s why we cater to divers of all levels, from beginners to experienced professionals. Our professional dive center, led by expert instructors, offers a range of courses and guided dives. If you’re new to diving, you can start with an introductory course that will teach you the basics of scuba diving in a safe and controlled environment.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
For more experienced divers, we offer advanced dive courses and guided excursions to some of the more challenging dive sites. Our instructors are knowledgeable and passionate about the local marine life, ensuring that every dive is not only safe but also informative and enjoyable.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Exclusive Diving Offer
To make your stay even more unforgettable, Hideaway is offering an exclusive diving package designed to enhance your experience both above and below the water. When you book a minimum 7-night stay, you’ll receive:
- 35% discount on room rates.
- Complimentary diving: 3 dives per person for 2 guests, allowing you to experience the beauty of the Maldives underwater world.
- Free meal plan upgrade: enjoy a complimentary upgrade from Bed & Breakfast to Half Board, or from Half Board to Full Board. Guests who prefer the White Platinum Plan (WPP) can avail it at a discounted rate.
This incredible offer provides the perfect opportunity to experience world-class diving while enjoying all the luxury and comfort that Hideaway Beach Resort & Spa is known for.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Combinable Offers for Even More Value
This diving offer can also be combined with our Anniversary and Honeymoon offers, allowing you to create the perfect celebration package. Whether you’re celebrating a milestone or simply seeking a romantic getaway, this offer ensures that you can enjoy the best of both worlds – luxurious accommodations and unforgettable diving adventures.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Terms & Conditions
- This offer is available exclusively for bookings made through the official Hideaway Beach Resort & Spa website using a specific booking code.
- The offer cannot be combined with other promotions available on the website or through other channels, nor can it be redeemed for cash.
- All dives are subject to weather conditions, ensuring the safety and enjoyment of all guests.
- Black-out dates: This offer is not available from 24th December 2024 to 9th January 2025.
To book this exquisite offer, use the Promo Code: SCUBA24FD
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Hideaway is not just a resort; it’s a sanctuary for those seeking peace, adventure, and luxury. With spacious villas, private pools, and world-class dining options, the resort offers everything you need for a perfect holiday. From tennis, golf, gym, cycling to the exquisite underwater activities, unique dining options, Hideaway has something for everyone. And for diving enthusiasts, it provides an unparalleled opportunity to explore some of the most beautiful dive sites in the world.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
Our dive center is fully equipped with state-of-the-art gear, ensuring that every dive is safe, comfortable, and enjoyable. Our instructors are passionate about the underwater world and are eager to share their knowledge with you, whether it’s your first dive or your 100th.
Email: reservations@hideawaybeachmaldives.com / Call: +960 650-1515 / Website: www.hideawaybeachmaldives.com
The Ultimate Dive Adventure Awaits
If you’re looking for an unforgettable diving holiday in the Maldives, look no further than Hideaway Beach Resort & Spa. With over 30 dive sites, unique marine life, and exclusive offers, we provide the ultimate underwater experience. Whether you’re celebrating a special occasion or simply seeking adventure, our diving package offers exceptional value and incredible memories.
Book now through our official website to take advantage of this exclusive offer and prepare for the dive adventure of a lifetime.
Email: reservations@hideawaybeachmaldives.com
Call: +960 650-1515
Website: www.hideawaybeachmaldives.com
Welcome to Day 5 of Scubaverse.com’s week-long Christmas Gift Guide!
Struggling to find the perfect gift for that special scuba diver in your life? Read on for Team Scubaverse’s pick of this season’s must-have Christmas gifts.
Every day this week, we are publishing a special Christmas Gift Guide full of different gift ideas that are all ideal for divers, so you’re sure to find something that’s perfect. Take a look at today’s selection below…
SlipIns DiveSkins
Team@slipins.com / www.slipins.com / SlipIns Facebook / SlipIns Instagram / SlipIns Pinterest
DiveSkins are perfect for scuba diving, snorkeling, swimming, paddling, surfing, and all water sports. It shows up beautifully in pictures under water.
This tight-fitting, tailored lycra suit offers maximum comfort. stretchy, breathable, fast-drying fabric with the world’s best sun and stinger protection.
SlipIns are:
*Ultimate 50+ UPF sun protection
*Abrasion protection.
*Quick dry, breathable, soft fabric
*The ultimate stinging critter protection
Save 10% on your order if you mention you saw this ad in Scubaverse in your order note!
SAVE YOUR SKIN…WEAR OUR SKINS
Team@slipins.com / www.slipins.com / SlipIns Facebook / SlipIns Instagram / SlipIns Pinterest
Diving Books from Miflex Hoses
sales@miflexhoses.co.uk / www.miflexhoseshop.co.uk / miflexhoseshop.co.uk/acatalog/Diving-Books.html / Miflex Hoses on Facebook
We stock a great range of Diving & Underground book titles, ideal to add to any order or simply buy as a gift for a friend.
Titles we have include:
Shipwrecks of the Dover Straits, Adventures Underground, Pioneers Beneath the Peak, Dive Truk Lagoon, Underwater Potholer, Images Below & many more.
From Authors including:
Stefan Panis, Martyn Farr, Duncan Price, Ron Young, Rod Macdonald, Chris Howes
Visit our website for more details.
sales@miflexhoses.co.uk / www.miflexhoseshop.co.uk / miflexhoseshop.co.uk/acatalog/Diving-Books.html / Miflex Hoses on Facebook
OrcaTorch D710 Dive Light – now available in pink!
sales@sea-sea.com / www.orcatorch.com / OrcaTorch on Facebook / OrcaTorch on X / OrcaTorch on YouTube
Already available in Black, Green, Red and Blue, the D710 Dive Light from Orcatorch is now available in Pink too.
Whether you’re a recreational or a professional diver, you’ll find the OrcaTorch D710 dive light useful in your underwater activities.
With max 3,000 lumens, the D710 is one of the strongest torches in its class. You also have plenty of brightness settings to choose from if you prefer less power.
It runs on one OrcaTorch 21700 5000mAh rechargeable battery with a Type-C charging port, easier for you to charge it anywhere. Now it offers five exterior colour options: Black, Green, Red, Blue, and Pink, to satisfy your diverse needs.
Featuring:
* Uses Luminous LED, max 3000 lumens
* Uses 1 * 21700 Li-ion battery
* 6° beam angle
* Offers four exterior colour options: Black, Red, Green and Blue
* Easy operation with side titanium alloy push-button switch
* Safe lock function, prevents mis-operation
* Intelligent Over-Heat protection
* Battery indicator
* Water pressure resistant construction, depth rated to 150 meters
* Reverse polarity protection, to protect from improper battery installation
* Over-discharge protection function
* Constructed from high-strength A6061-T6 aluminum
* Mil-Spec Type III hard anodized finish for durability and corrosion resistance
* Two sides coated toughened glass with high water pressure resistance under deep water
Sea & Sea is the home of OrcaTorch and other leading diving brands in the UK.
sales@sea-sea.com / www.orcatorch.com / OrcaTorch on Facebook / OrcaTorch on X / OrcaTorch on YouTube
Scubapro Luna 2 AI Dive Computer
Scubapro Europe Website / Scubapro USA Website / Scubapro on Facebook / Scubapro on Instagram / Scubapro on YouTube
SCUBAPRO, the world’s premier manufacturer of high-quality scuba diving equipment, introduces its second generation Luna 2.0, an easy-to-read, intuitive dive computer loaded with easy-to-use features and available in two versions, the Luna 2.0 and Luna 2.0 AI with wireless air integration.
Designed for new and casual recreational divers, the low-profile Luna 2.0 sits comfortably on the wrist. Its oil-filled plastic housing helps ensure reliable performance to depths of 120 meters. A large widescreen display features a high-contrast black and white matrix-segment LCD with full-sized characters for easy reading in all dive conditions. An intuitive menu and simple two-button interface lets the diver navigate the system with ease, aided by clearly marked screen prompts. The LUNA 2.0 offers two algorithms – Predictive Multi-Gas Bühlmann ZH-L16 ADT MB PMG or ZH-L16 + GF PURE, plus 21-50% nitrox compatibility and three selectable gasses for open circuit diving. Three dive modes are available – Scuba, Apnea and Gauge – to suit a range of diving activities.
The Luna 2.0 AI (air integrated) offers the same easy-to-use features and functions as the standard Luna 2.0 plus adds wireless air integration. This not only enables to easily monitor ythe tank pressure, it also provides true remaining bottom time (RBT) and allows the air consumption to be factored into the decompression calculation. Also available with the Luna 2.0 AI is an optional integrated heart rate monitor that lets visually track the heart rate and skin temperature to help staying in the personal target zone.
Both Luna 2.0 models include personalized dive management functions like PDIS (Profile Dependent Intermediate Stops) which calculates an intermediate stop based on N2 loading, current and previous dives and breathing mixes, and Microbubble levels that give the option to adjust the level of conservatism in the algorithm to match the individual experience level, age and physical conditioning for a more enjoyable dive.
The soft silicone arm strap offers a comfortable fit on the wrist, plus bungee mounts on the corners of the housing allow for alternate attachment methods. A Bluetooth Low Energy interface enables the download of the dive data to any iOS or Android device or PC/Mac (firmware can be user-updated), and the CR2450 battery is rated for up to two years or 300 dives.
Scubapro Europe Website / Scubapro USA Website / Scubapro on Facebook / Scubapro on Instagram / Scubapro on YouTube
35% off Red Sea Liveaboard Scuba Scene in Spring 2025
info@oysterdiving.com / www.oysterdiving.com / Oyster Diving Facebook / Oyster Diving Instagram
Embark on the ultimate diving adventure aboard the Scuba Scene, the luxury liveaboard offering an unforgettable Red Sea experience. Known for its exceptional service, safety, comfort, and world-class dive sites, Scuba Scene is the ideal choice for divers of all levels.
Dive into crystal-clear waters teeming with vibrant coral reefs, exotic marine life, and awe-inspiring shipwrecks. From the stunning Ras Mohammed National Park to the famous Thistlegorm wreck, Scuba Scene brings you to the heart of the Red Sea’s best sites. With spacious cabins, gourmet dining, and a dedicated crew that ensures every detail is perfect, this liveaboard guarantees relaxation and adventure in equal measure.
Now is the perfect time to book! Save a massive 35% on any sailing between 3rd March and 28th April 2025. Whether you’re a seasoned diver or taking your first plunge, Scuba Scene promises an experience you’ll cherish forever.
Don’t miss this chance to dive the Red Sea in style and at an incredible price. Book your adventure today!
Tel: 0800 699 0243
info@oysterdiving.com / www.oysterdiving.com / Oyster Diving Facebook / Oyster Diving Instagram
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