At the end of 2018 the company Aggressor invited me to give a talk on how to behave and dive safely with tiger sharks, following the attack that a year earlier had cost the life on Cocos Island to an American diver and injuries to the guide who accompanied her.
First of all I must say that tiger sharks reappeared about twelve years ago in the environment of the island, after an absence of more than thirty, but until 2017 had not had any problems with them. Their behavior with the divers was the usual behavior of the other sharks, they passed more or less close, took sometimes a reconnaissance lap and went on their way disappearing into the blue. So the attack caught everyone by surprise.
It is uncertain which shark was responsible for the fatal encounter, but according to Carlos Sanchez, captain of the Okeanos II and Anibal Morales, both expert dive guides in the Cocos Island National Park, a month after the incident, a female shark was harassing a group of divers from the middle of the dive until they managed to get safely back to the boat. It was a young specimen, with clearly marked stripes on her back and well identified by a white spot on the front of her dorsal fin. She was described as having a long and slender body, and was soon christened among local divers as Lagertha, the semi-legendary Viking warrior wife of Ragnar Lodbrok, a character in a famous TV series (Vikings). Her behavior, according to those who have seen her, is different from the rest of her species. Tiger sharks, when they think of attacking or are about to come into contact with something that could be potentially dangerous for them, run the nictitating membrane to protect their eyes, but Lagertha is opening and closing the membrane as if it were an eyelid long before reaching the contact distance.
Since that time it seems that the same female has been involved in all the difficult encounters that have taken place, starting with the attack on a young man who defended himself by removing his gear and using it as a shield. Hannibal recounts that he has been harassed on several occasions, and Carlos has had to use at least three times the steel spike they are forced to carry, because Lagertha, far from being frightened, as soon as she fixes her attention on a group chases him until the last diver has left the water. Carlos' last encounter was after a tense dive under the permanent surveillance of the shark, when he had to emerge alone while the rest of the group remained under the protection of the reef. Lagertha forgot about the group and headed straight for him, and only his determined way of facing her with the spike in front dissuaded the animal from being the easy prey it was supposed to be.
It seems to be an extremely intelligent shark that prowls the divers until it finds the weakest or most defenseless one to prey on. And the most striking thing is that, according to one of the island's rangers, after hovering for a while around the group of divers he was accompanying, Lagertha disappeared and soon returned with a young male that began to imitate his behavior.
Considering the problem, the question was to establish a protocol to dive safely in case they found themselves in a similar situation again, and my proposal was the following: first of all, stay close to the bottom or the wall if the shark starts hovering during the dive. Avoid any sudden movements, do nothing to attract its attention and wait for it to lose interest. If it persists, and you have to start the ascent in open water, it is important to have a good hydrostatic balance, do not kick or brace in a way that encourages its curiosity and never lose sight of it. Couples should ascend back to back, never swim backwards putting the fins between you and the shark, always with your face forward and following it with your eyes wherever it goes. If it disappears into the blue, you must think that it will return, so you must constantly watch your surroundings to locate it as soon as it does.
The tiger shark is an animal that moves slowly during the day, so in case it starts a more extreme approach, you can push it away with a steel rod (with which the guides and some clients dive) or with the same hands pushing its head down when it closes its eyes, although I recognize that this requires a lot of cold blood. If you are already on the surface, it is more practical to take off the BCD with the tank and place it in front of your body as if it were a camera housing. In this case, it is advisable to release the weights and always keep the regulator in your mouth and your head underwater without losing sight of the animal. It will attack, if it does, when it thinks its prey is unattended. On the other hand, the "pangueros", drivers of the pangas, already know that if they see a group of surface divers lying face down with their heads in the water, it is because there is a tiger nearby, and in that case they alter the order of retrieval: first they pull the divers out of the water and then retrieve the equipment that remains floating.
I don't know if by luck or by misfortune, after twenty-two dives we didn't manage to meet Lagertha to test the protocol, but there it remains for those who follow us.
It is a good time to make it clear that diving with sharks without knowing entails the risk of death. I dive with them, I do what I can to protect them, I have never felt in danger, but I don't let my guard down either. You have to pay attention to the indications of the experts and do not ignore the safety rules because if you are careless they can kill you. In the water, they are always the masters...
