Seventeen years ago, Alex Kerstitch and three other photographers headed out to the Sea of Cortez on Mexico's Pacific coast to try to document the behavior of squid in their natural habitat. During one night dive, a passenger aboard the ship hooked a 14-foot thresher shark, and the four photographers jumped in. As the photographers' flashes went off, they noticed dozens of other lights streaking around them in the water. One of the red and white streaks—a jumbo squid more than six feet long—flung itself onto the weary shark, ripping a fist-sized chunk of flesh from its head. Then a tooth- and sucker-tipped tentacle lashed out and grabbed Kerstitch’s head and swim fin, pulling him down toward its birdlike beak. Kerstitch frantically dug his fingers into the squid and it released him long enough for him to scramble back onto the boat.