Aquarium officials have likened the act, which is a first at the aquarium, to a "turf war."
"Sharks have their own territory," an aquarium staffer told Reuters on Friday. "However, sometimes, when they bump into each other, they bite out of astonishment."
But from the aquarium keepers to the crowds pressed against the glass, to the YouTube gawkers, there seems to be plenty of astonishment to go around.
Could this have happened in the wild?
Compared with the sprawling ocean where these sharks belong, there certainly isn't much turf to go around. According to a South Korean tourism website, COEX hosts around 40,000 "sea creatures" all apparently tucked into around 130 tanks, with an additional 90 tanks for breeding.
Maju Tak Gentar / YouTube