A shark-diving trip off Mexico's Guadalupe Island almost ended in disaster recently when a 13-foot (3.9m) great white jammed its body inside the open top of the dive cage, and severed the divers' air supply line in the process. The nightmare scenario received a lot of media attention, but what was largely ignored in the coverage was the root cause: the dangerous incident happened because dive operators did something illegal.

After the 13-foot female shark (known locally as "Big Mamma") bit the divers' air hose, one of the crew members managed to return air pressure to the "hookah-style" breathing system by opening a safety valve at the base of the cage. But the dangerous experience was far from over: in the moments that followed, the shark became stuck in the cage's open balcony, and was inadvertently wedging herself deeper as she struggled to break free of the bars. The divers remained trapped beneath her during the ordeal.

"It's hard to put into words the thoughts and feelings that went through my head," writes Bluewater Dive Travel operations director Katie Yonker, one of the divers involved in the incident. "The first minute or so felt like a horrific earthquake underwater, and I kept thinking, 'we just need to wait this out.' But in the back of my head I feared the cage would break apart and this would be the end for me. I was calm, but felt very, very sad." 

Thankfully, everyone – including the shark – was eventually freed, to the dive team's credit. But this situation could have been avoided altogether.

Guadalupe's waters draw in some of the largest great white sharks in the world, and thanks to the appearance of the famous "Deep Blue", diving here has become more popular than ever. In many ways, this is great news: exposing the public to sharks in their natural habitat can help to rehab a reputation much dented by films like Jaws. But this can only happen if divers follow the rules – including the rules that apply to baiting the water.

Many operators chum (or bait) around a dive site to draw sharks near, but baiting over (or on) a shark-diving cage is strictly prohibited in Guadalupe. The outfit involved here, operating aboard the luxury vessel Nautilus Explorer*, ignored these regulations. In doing so, they endangered the lives of four people – and they put a magnificent white shark at risk. Alarmingly, this is the third time we've seen such behaviour from the seasoned operator (though one video has since been removed from YouTube).

"Like in many places, people don't follow the rules – which aren't even necessarily for their own protection, but that of the animals," shark biologist Dr Christopher Lowe told us at the time of the last incident. Great whites might be top predators, but they can easily become injured by cages, as seen in another dive-gone-awry, which was also filmed recently in Guadalupe:

In this situation, the operators – who have a history of managing bait properly – reacted correctly by opening the top of the cage right away. But despite their best efforts, the shark most likely suffered blunt force trauma to the right side gills while thrashing around. (Official statement found here.)

It's a common misconception that baiting close to (or on) the cage is the only way to experience a phenomenal shark encounter. Renowned white shark diver George T Probst's photographs from Guadalupe have attracted more than 133,000 followers on Instagram – and none of those images was captured during a dive where the cage held a chum bag. "Baiting is going to attract sharks, and the goal should never be to attract sharks directly toward a cage," he says.

Rather oddly, Nautilus Explorer's own website supports this line of thinking:

"We don't need to use chum at depth; the sharks are already there. We have seen up to six great whites at once circling the cages. Without chum these great whites are more relaxed, exhibit MUCH more curiosity, and come in MUCH closer to the cages. Best of all, our cages are double-deckers, which means you can venture onto the upper deck and outside the bars** to truly go face-to-face with great white sharks out in the open."

A chum bag, however, is clearly visible in the photographs from their recent disastrous dive, and a trip report from Yonker confirms the use of bait on the cage itself. "The submersible cages descend with one bag of fish chum, which entices sharks with its scent," she writes.

Some have suggested that because chum bags simply hold bait, operators who use them are not explicitly "feeding" white sharks – and this is exactly the kind of loophole that makes enforcing the rules such a challenge. This argument certainly doesn't hold up against the 51-page Guadalupe shark-diving code of conduct, which was put in place by the National Commission of Natural Protected Areas (CONANP), one of the area's ecotourism governing bodies.

Its rules clearly stipulate that bait lines must not touch the cage (or pass over the top). They also require operators to immediately remove the line from the water upon a shark's close approach, and prohibit the use of bait on a line shorter than 40 feet (12m). In recent years, many dive outfits have been opting to bring CONANP reps along on their charters in order to prevent serious mishaps like this one. Had this been the case aboard the Nautilus, we may have seen a very different outcome.

Sharks are certainly not the monstrous murder-machines they're often made out to be (that's something we pride ourselves on setting straight), but they can be dangerous and should be respected. Would you set off on a big-cat safari with a bleeding chunk of dead wildebeest tied to your vehicle? Not likely.

In Mexico, the great white is classified as a threatened species, and many of the white sharks in Guadalupe are female. It takes more than a decade for these animals to reach sexual maturity, so the loss of even one adult female can do lasting damage to a population.

Though encounters like this one are rare, the unfortunate reality is that every negative interaction with a shark can greatly impact the public's perception of these animals, so we should be doing everything we can to prevent them. In these situations, a few cases of misconduct can hinder progress made by an entire industry. "Encounters such as this are often sensationalised as man-eating shark attacks," notes Yonker. "To be clear, this was in no way a shark attack. It was a shark enticed by the scent of tuna, not humans. I suspect (and hope) that this incident prompts some changes in the operations."

Another member of the party, identified only as David agrees. "My ultimate goal is that we humans will realise the value of these beautiful creatures and do the right thing by protecting them."

* The leisure vessel described in this piece should not be confused with the NOAA research vessel, EV Nautilus.
** It's worth noting that "venturing outside the bars" is also illegal.

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