Shortly after midnight on July 30, 1945, the USS Indianapolis was cruising off the coast of the Philippines when disaster struck. Torpedoes fired by the Japanese Imperial Navy pierced the hull of the tanker, and within twelve minutes, the crew of 1,195 sailors found themselves afloat in the open ocean — the natural habitat of the oceanic whitetip shark.

As part of the Shark Week segment Sharkwrecked, James Glancey, formerly of the United Kingdom Special Forces, and shark attack survivor-turned-shark expert Paul de Gelder attempted to recreate what is now described as one of the biggest mass shark attacks in history. The experiment began by blowing up a ship to simulate a torpedo attack. The experiment spanned a period of two days, during which time the two men floated unassisted in the open ocean.

Shark expert and co-leader of Florida International University’s Predator Ecology and Conservation Lab, Yannis Papastamatiou, tells Inverse the behavioral instincts of the oceanic whitetip shark actually made de Gelder and Glancey the perfect prey for the oceanic whitetip — much like the sailors aboard the USS Indianapolis.

shark week oceanic white tip
The oceanic whitetip shark usually weighs around 200 pounds.

“The thing to remember about oceanic whitetips is that they basically live in what we could consider the oceanic equivalent of the desert,” Papastamatiou says. “We can see behavioral adaptations they have to deal with that. They just seem to be a very curious species of shark.”

It is this behavioral tendency toward curiosity that has, in part, led to the decline of these sharks over the years. Several studies between 2004 and 2015 documented declines in oceanic white tip populations between 53 and 70 percent.

But it’s also what made them so dangerous to the survivors aboard the USS Indianapolis as well as to what made them such a threat to de Gelder and Glancey during the filming of Sharkwrecked. When the Discovery team blew up the boat at the outset of their experiment, it sent a series of sound waves to which the oceanic whitetip is particularly sensitive throughout the water.

USS Indianapolis (CA-35) off the Mare Island Naval Shipyard on 10 July 1945 (19-N-86911)
The USS Indianapolis in July of 1945, weeks before it sunk

“We have good evidence that when incidents occur they are able to respond quite quickly,” Papastamatiou says. All sharks have inner-ears, he explains, that become attuned to low-frequency sounds like massive explosions.

When a big ship like the USS Indianapolis goes down, it creates stimuli that travel quickly through the water, creating small pressure changes that pique the shark’s interest. This, combined with its speed and natural curiosity, often means that the oceanic whitetip is the first to arrive on the scene.

De Gelder says that he experienced these behavioral instincts, honed by years of natural selection, during the course of filming. “These sharks move so quickly,” he tells Inverse. But it also gave him a decently good idea of what it might have been like to battle these forces back in 1945, as the floating sailors waited for salvation that, for many, never came.

“It was so exhausting,” he says. “The mental and emotional toll of it all.”