Ground-up bait, also known as CHUM, is a type of bait used in fishing. It is made up of ground-up fish parts, such as heads, tails, and entrails, which are mixed with other ingredients to create a paste-like substance. This mixture is then spread in the water to attract fish. CHUM is often used in combination with other types of bait, such as live bait or artificial lures, to increase the chances of catching a fish.