Chumming is the practice of luring animals, usually fish

Fish

Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

 or shark

Shark

Sharks are a type of fish with a full cartilaginous skeleton and a highly streamlined body. The earliest known sharks date from more than 420 million years ago....

s, by throwing "chum" into the water. Chum

Fishing bait

Fishing bait is any substance used to attract and catch fish, e.g. on the end of a fishing hook, or inside a fish trap. Traditionally, nightcrawlers, insects, and smaller bait fish have been used for this purpose...

 often consists of fish parts and blood, which attract fish, particularly sharks due to their keen sense of smell.

Also known as rubby dubby (West Country and Yorkshire, UK), shirvey or chirvey (Guernsey, Channel Islands), berley or berlying (Australasia), and bait balls.

Chumming is illegal in some parts of the world, such as Alabama

Alabama

Alabama is a state located in the southeastern region of the United States. It is bordered by Tennessee to the north, Georgia to the east, Florida and the Gulf of Mexico to the south, and Mississippi to the west. Alabama ranks 30th in total land area and ranks second in the size of its inland...

, because of the danger it can pose by conditioning sharks to associating feeding with the presence of humans.