An aggressive attack on prey by a group of sharks. The resulting boiling and bloody sea results in the sharks wildly attacking any creature nearby - even their own kind.
This term applied initially specifically to shark attacks and was coined in the mid 20th century; for example, here's an early citation from a piece by T. Lineaweaver in Sports Illustrated, February 1960:
"When sharks are in a feeding frenzy, the man who hangs too close to the surface to grimace, may lose his head - face, grimace and all."
It wasn't long before that vivid imagery was began to be used in other contexts. In Science, April 1972 we have:
"It would be rash to take them as evidence of a coherent movement to cripple the law. But what worries environmentalists ... is that a feeding frenzy may develop among federal agencies once a few loopholes have been opened in the law."
See also - lager frenzy.
See other phrases that were coined in the USA.