There are many legends and, in more recent times, news reports of dolphins coming to the aid of humans in peril. Victims of shark attacks tell of dolphins rushing to the scene and repelling sharks with high-speed blows, and drowning swimmers have testified that dolphins lifted them to the surface to breathe.
A dolphin's sonar penetrates a human body, making our skeletons, lungs and heart visible (dolphins are even able to hear an embryo's heartbeat, and are especially fascinated by pregnant women). As fellow mammals, it is possible that dolphins recognise similarities in humans, and understand that we are vulnerable to drowning and attacks from predators.
According to Dr Diana Reiss, one of the world's foremost dolphin experts, what we can say is that rescue behaviour in dolphins is not automatic or purely instinctual. "Dolphins make conscious decisions about when they intervene – they weigh up the situation and are selective about who and in which circumstances they help," she says.
Hardy Jones, a wildlife filmmaker and longtime campaigner against the Japanese dolphin slaughters, is one human who has benefited from dolphins' ability to detect our distress. In 2003, Hardy was filming a group of dolphins when he noticed a large shark approaching him in attack mode. Four dolphins swept in to protect him. Hardy was able to capture the rescue on camera (you can view his footage above).
Dolphins sometimes repeatedly ram sharks to kill them or drive them away, but are rarely aggressive towards humans, even when provoked. In fact, dolphins are known to form protective rings around swimmers and surfers to guard them from sharks.
In 2004, the Guardian reported that four people were saved in New Zealand from a great white shark by a pod of dolphins which swam circles around them for forty minutes until the shark lost interest and swam away.
"They started to herd us up, they pushed all four of us together by doing tight circles around us," Rob Howes, who had taken his daughter and her two friends for a swim, told the New Zealand Press Association.
At first, Howes thought the dolphins were merely being playful, and he tried to swim away from the group. But two of the larger dolphins rushed to him and ushered him back into their protective circle. It was at this moment that Howes noticed what the dolphins seemed to be concerned about – a 3 metre great white shark heading toward the group.
"I just recoiled," he said. "It was only about two metres away from me, the water was crystal clear and it was as clear as the nose on my face. They had corralled us up to protect us".
You can check out a reenactment of the rescue created for the BBC documentary "Saved by Dolphins" below.
Equally indebted to dolphins is Davide Ceci, a teenage boy who fell off the side of his parent's boat. Having never learned to swim, Davide was minutes from drowning when Filippo, a dolphin well known to locals In Manfredonia in south-east Italy, swam up underneath him and began pushing him up out of the water.
"When I realised it was Filippo pushing me, I grabbed onto him," Davide told Scotland's Daily Record. Filippo drew close enough for Davide's father to reach down and pull Davide to safety.