scumboard

[ skuhm-bawrd, -bohrd ]
/ ˈskʌmˌbɔrd, -ˌboʊrd /

noun

a board or strip of material partly immersed in flowing water to hold back scum.

Origin of scumboard

First recorded in 1895–1900; scum + board
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019