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That’s wrong: misconceptions about overhead diving

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By: John Bentley & Brian Shreve

The interwebs are a great place to pick up some great, and some not so great, information.  Internet cave divers seem to enjoy spouting off opinions based loosely on nothing. This is particularly scary considering the fragility of the cave community and the necessity for standardization in cave diving. Spend a little time on the various scuba related websites, and it’s amazing some of the just plain wrong things you can read!

Here are just a few of them we’ve recently found:

The Rule of 1/6th isn’t appropriate for gaining real experience

This is, unfortunately, a popular one in the North Florida area: The idea that 1/6th doesn’t give the Intro Cave diver enough distance to utilize their newfound awareness, conservation and buddy skills. That’s just not the case. 1/6th gives adequate gas, even for the biggest gas guzzler, to get acquainted to a cave system in a way that exposes them to overhead stress with emphasis on line awareness, buddy procedures, communication, and gas management. It essentially eliminates navigation stress through mainline navigation only, reduces time/distance stress and eliminates most decompression obligation stress.

If 1/6th diver’s gas consumption rates aren’t adequate for getting a few hundred feet into the cave that shows that their comfort level, fitness, and streamlining are not to the level needed to be that far into a cave anyway. While all divers breathe at different rates, and that’s a physiological issue, even the best trained divers double their gas consumption rate under stress. Putting a high volume breather further into a cave without mastery of stress management is asking for trouble.

Visual Jumps are OK

It’s only 3 feet!
This cave never silts out!
I’m familiar with this passage…

Holy moley, no! This one defines all logic. The time it takes to install a jump or gap, a matter of seconds, nullifies all reasons that this would be ok. All overhead dives should be planned for a total loss of visibility, whether through siltation, total light failure or mask loss. If viz is gone finding the gap will be difficult, objectively more difficult than following a line.

Primary lines are optional in tourist caves

This system will spit me out if I’m lost!
Close to open water is close enough!

This one goes back to the previous point. Just no! Tourist caves, like Ginnie and Peacock, that don’t have a line that goes to open water, are no safer than a virgin system. A cavern full of students can quickly make Peacock impossible to navigate. Plenty of individuals have perished in the forward section of a system because they couldn’t clearly find an exit. Just to clarify – If you’re in trouble, running low on gas after a reg failure in low vizibility, do you really want to hit the end of the line, let go, and hope for Mama Ginnie to spit you out? If the answer to that is yes: please, please, take up racquetball instead of cave diving.

It annoys everyone when caverns are a mess of lines, and yes, sometimes that makes it more dangerous. The only solution for a clear exit, where the line runs to the open water, is for cave divers to speak up and have lines extended to open water. This is an issue with land owners not properly restricting access to non-overhead divers. If the site is not open water appropriate (Ginnie for example) then it needs to be restricted to overhead divers only and the guideline should be extended to open water to prevent too many lines. Issues like this are very isolated to certain sites in North Florida and, despite the ease of fix, have spawned an alternate pattern of thinking towards continuous guidelines in cave diving. While every cave is unique and beautiful no cave merits entry without the ability to very easily navigate to the surface with visibility loss.

The Rule of 1/3rds is always appropriate

This is normalization of deviance at its best. The rule of thirds is not always appropriate. When exerted you will use substantially more gas. Long strenuous swims using substantially more gas, or possibly gas sharing, will not work with the rule of thirds. Stages do cause drag and aren’t always appropriate but with long swims in low flow systems they’re a necessary parachute. The “Grand Traverse” in Peacock is often done on thirds and while that seems appropriate to some the margin for error is little with only the gas in a couple sets of mains. A setup dive for longer swims or scooters should include a stage cylinder(s) drop for use as a safety cylinder. This goes back to the basics of dive planning and gas management. We’ve seemed to have forgotten that there are reasons behind the 1/3 rule.

These are just a sample of researched and proven techniques being put to the wayside for stories being shared between divers. The data pools aren’t huge in cave diving, but they’re large enough to set our safety standards. Ignoring these basic guidelines puts us all at risk.


To find out more about International Training, visit www.tdisdi.com.

From its humble beginning in 1994 to today, the group of training agencies Scuba Diving International (SDI), Technical Diving International (TDI), and Emergency Response Diving International (ERDI) form one of the largest diving certification agencies in the World – International Training. With 24 Regional Offices servicing more than 100 countries, the company today far exceeds the original vision the founders had when they conceived the idea on a napkin, sitting at a kitchen table in the early 1990’s.

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Mares & SSI launch new promotion

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SSI expands financial support to SSI Members worldwide. 

2020 has been an unusual and challenging year for the entire world, especially the diving and travel industry!  To weather the crisis, SSI immediately jumped into action to help Training Centers and Professionals around the world.  

In response to COVID-19, SSI launched the No Water, No Problem Campaign, put Final Exams online, and held hundreds of Webinars to train Professionals on how to use distance learning to teach the dry Specialties online. The FREE SCIENCE OF DIVING promotion resulted in SSI Training Centers worldwide register over 50,000 FREE DIGITAL KITS, funding more than $3.5 MILLION IN RETAIL VALUE. Additionally, SSI introduced an aggressive DOUBLE PRO REWARDS incentive to help SSI Professionals compensate 2020 Renewal Fees and reduce those for 2021. Currently, the WE WANT YOU Crossover promotion aims to fill the industry need for instructors and strengthen the entire SSI Professional community.

Now, in conjunction with Mares, SSI is launching the GO DIVING – PROTECT YOURSELF. OWN EQUIPMENT Promotion, which includes a FREE SSI EQUIPMENT TECHNIQUES DIGITAL KIT. This new campaign strives to motivate divers worldwide to go diving and buy equipment. Look for more information on this next retail support campaign within the next few days.

“These are just a few examples of how we have supported and are continuing to support our Training Centers, Professionals, and divers worldwide. To provide even more economic security and help in business recovery, WE WILL NOT INCREASE PRICES FOR 2021. While travel was restricted and some key resort areas completely locked down, SSI mainly focused on supporting domestic markets with retail-driven incentives. Now, in this next re-opening phase, we need to shift gear and assist resort markets that have no local diving community and are 100% dependent on the traveling diver. Therefore, SSI will grant certain special conditions and delayed payment options to specific resort markets which have been locked down for longer than six months or suffered from closed borders,” stated Guido Waetzig, SSI CEO.

Guido Waetzig, SSI CEO, explains further, “To financially support these needed investments which directly benefit SSI Members and to protect the health of our valuable members and staff, we will forego all 2021 Trade Shows over the next 12 months. Despite international uncertainty, every time we experience one of these events, the entire SSI Network emerges stronger and more resilient. Be assured, SSI is your trustful partner within the Diving Industry!”

For more information about SSI visit their website by clicking here.

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Photo Gallery: Shark Diving in The Bahamas

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In our Gallery feature, we let the photos tell the story… Each Gallery showcases a selection of outstanding images on a chosen theme, taken by our Underwater Photography Editor Nick and Deputy Editor Caroline of Frogfish Photography. This time they look at Shark Diving in The Bahamas.


The Bahamas offers some of the very finest shark diving experiences in the world. The islands have protected sharks in their waters creating one of the first Shark Sanctuaries in the world. Several species of shark can be seen and photographed, with each island offering a different type of shark diving, making this destination the perfect place for a multi-island, multi-shark trip of a lifetime.

Great Hammerhead Shark diving in Bimini

Bull Sharks in Bimini

Tiger Shark off Grand Bahama

Oceanic Whitetip Shark off Cat Island

Nurse Shark off Abaco

Caribbean Reef Sharks off New Providence

Lemon Sharks off Grand Bahama

For more images from The Bahamas and around the world, visit the Frogfish Photography website by clicking here.

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