Grindylow 'lure'

"The Grindylow 'lure' is an adapted fleshy growth resembling a worm, which, when moved, is irresistible to fish. When resting above the water's surface, the lure is known to attract birds, mammals, and, occasionally, curious children."

- Aquatic Wonders of Yorkshire: A Wizard's Field Guide

The 'lure' of a Grindylow is a worm-like appendage that grows on the creature's head. This adapted anatomical feature makes it easier to lure prey such as fish, or even birds and some mammals — on occasion, Grindylows are known to have attracted the attention of small children with it.