The display was described in the 1960s at Eniwetok Atoll after divers found that some sharks became agitated when approached in confined water. The elements are consistent: the pectoral fins are pushed down and stiff, the head lifts, the back arches, and the shark swims in a stiff, rolling, laterally exaggerated path.
Intensity scales with how cornered the animal is. Displays are strongest when a shark is pursued or blocked against a reef wall or the surface, and weakest in open water where escape is available. A shark that continues to be pressed may then make a rapid slashing bite and withdraw.
The common misreading is to treat this as aggression toward a food item. It is defensive signalling, and it appears in a species that is otherwise unremarkable in its interactions with divers. Grey reef sharks are now Endangered, having declined sharply on reefs with any appreciable fishing pressure.